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LIBRARY 

OF  THK 

UNIVERSITY  OF  CALIFORNIA. 

GIFT    OF 

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Class 


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Spectra,  Sup.   221. 


ECLECTIC  EDUCATIONAL  SERIES. 


THE   ELEMENTS 


CHEMISTRY 


INORGANIC  AND  ORGANIC 


BY 


SIDNEY  A.  NORTON,  PH.D.,   LL.D., 

Professor  in  the  Ohio  State  University. 


VAN  ANTWERP,  BRAGG  &  CO. 

CINCINNATI  NEW    YORK 


ECLECTIC  EDUCATIONAL  SERIES. 


p 

\9 


HIGH  SCHOOL  AND  COLLEGE  COURSE  OF  STUDY. 


White's  New  Complete  Arithmetic. 
Ray's  New  Higher  Arithmetic. 
Ray's  New  Algebras. 
Ray's  Higher  Mathematics. 
Schuyler's  Complete  Algebra. 
Eclectic  School  Geometry. 
Schuyler's  Principles  of  Logic. 
Schuyler's  Psychology. 
Duffel's   {Hennequirf  s)    French 

Method. 

Duffet's  French  Literature. 
Hepburn's  English  Rhetoric. 


Thallieimer'  s  Historical  Series. 
Norton's  Natural  Philosophy. 
Norton's  Elements  of  Physics. 
Norton'' s  Elements  of  Chemistry. 
Eclectic  Physiology. 
Andrews' s  Elementary  Geology. 
Andreivs's  Manual  of  the   Consti- 
tution. 

Gregory's  Political  Economy. 
Studies  in  English  Literature. 
Hewetfs  Pedagogy. 
Bartholomew's  Latin  Series. 


DESCRIPTIVE    CIRCULARS    ON    APPLICATION. 


COPYRIGHT,   1878,  BY  VAN  ANTWERP,  BRAGG  &  Co. 
COPYRIGHT,   1884,  BY  VAN  ANTWERP,  BRAGG  &  Co. 


ECLECTIC  PRESS: 

VAN   ANTWERP,    BRAGG  &  CO. 


PREFACE. 


THIS  work  is  intended  as  a  text-book,  not  as  a  manual  for 
reference.  The  author  has  endeavored  to  select  such  chemical 
phenomena  as  represent  the  cardinal  principles  of  the  science, 
giving  preference  to  those  which  are  easily  reproduced  by  the 
student,  and  which  enter  into  the  affairs  of  common  life.  To 
attain  this  end,  he  has  omitted  many  excellent  experiments  which 
require  the  use  of  expensive  apparatus,  and  has  substituted  others 
which,  if  less  "classical,"  are  of  easier  application. 

The  engravings  represent  well-fashioned  apparatus;  but  no  one 
ought  to  be  deterred  from  attempting  an  experiment  because  he 
has  not  the  exact  shaped  figure.  Any  drug-store  or  kitchen  will 
afford  bottles  and  tumblers,  which  may  be  used  in  place  of  flasks 
and  beakers.  In  some  way,  the  experiments  ought  to  be  tried. 
Glass  tubing,  rubber  tubing,  and  good  corks  are  the  first  requisites, 
and  are  easily  obtainable.  The  most  essential  thing  in  experi- 
menting is  the  experimenter.  He  should  know  (1)  what  he  pro- 
poses to  do;  (2)  what  are  the  means  at  his  command;  and  (3)  how 
he  intends  to  use  them.  He  must  bear  in  mind  that  a  Chinese 
fidelity  is  not  required  —  e.  g.,  that  one  alkali  may  replace  another, 
or  that  corresponding  salts  may  be  substituted  one  for  another  as 
occasion  requires.  Nevertheless,  he  must  remember  that  Chemistry 
is  exact  in  her  methods;  (1)  that  careless  manipulation  will  not 
secure  good  results;  and  (2)  that  such  words  as  neutral,  acid,  basic, 
excess,  must  not  be  neglected. 

237443  -w 


iv  PREFACE. 

As  regards  nomenclature,  the  author  has  endeavored  to  follow 
as  closely  as  possible,  in  a  work  of  this  size,  the  rules  of  the  Lon- 
don Chemical  Society.  Old  and  well-known  names  have  been  re- 
tained because  of  their  common  use. 

As  regards  notation,  it  must  be  borne  in  mind  that  all  formulae 
are  alike  subject  to  change.  No  greater  mistake  can  be  made  than 
that  any  formula  (except  a  binary)  tells  the  whole  truth  about  a 
molecule,  or  that  any  formula  which  correctly  represents  the  per- 
centage composition  of  a  substance  may  not  be,  at  times,  available 
in  fixing  in  the  mind  of  the  student  the  fact  to  be  remembered. 
The  author  has,  therefore,  used  the  formula  that  appeared  conve- 
nient at  the  time;  and  feels  that  an  experience  of  twenty  years' 
teaching  warrants  him  in  advising  his  fellow-teachers  not  to  at- 
tempt to  place  theory  above  practice.  The  use  of  theory  is  to 
enable  one  to  generalize  known  facts  and  predict  new  ones;  the 
business  of  teaching  is  to  enable  the  student  to  master  facts,  prin- 
ciples, and  laws  already  ascertained  and  established. 

The  Science  of  Chemistry  is  not  an  easy  one  to  master;  but  it 
will  well  repay  careful  study,  not  only  by  reason  of  the  evident 
importance  of  the  facts  it  presents,  but  also  as  regards  its  special 
discipline  in  Education.  It  is  hoped  that  the  selection  of  facts 
herein  presented  are  such  as  will  be  found  useful  in  themselves, 
and  also  well  calculated  to  develop  the  principles  upon  which  the 
Science  is  founded. 

The  present  edition  has  been  thoroughly  revised,  and  has  also 
been  enlarged  by  the  introduction  of  a  dozen  chapters  treating  of 
Organic  Chemistry. 

The  author's  thanks  are  due  to  Mr.  CURTIS  C.  HOWARD,  of 
Columbus,  and  to  Mr.  PLINY  BARTLETT,  of  Cincinnati,  for  material 
assistance  rendered  during  the  passage  of  the  book  through  the 
press.  If  any  errors  are  found  which  have  escaped  their  very 
careful  proof-reading,  the  author  will  be  obliged  to  any  one  who 
will  take  the  trouble  to  point  them  out. 

COLUMBUS,  OHIO,  Nov.  1,  1884. 


TABLE  OF  CONTENTS. 


INORGANIC  CHEMISTRY. 

PAGE 

CHAPTER  I.— LAWS  OF  CHEMICAL  COMBINATION  ...  7 

II.— CHARACTERISTICS  OF  CHEMICAL  AFFINITY     .  26 

III.— CHEMICAL  PHILOSOPHY  AND  NOMENCLATURE  50 

"           IV.— WATER  AND  ITS  ELEMENTS     ....  71 

"            V.— THE  CHLORINE  GROUP 90 

"          VI.— THE  SULPHUR  GROUP 108 

"         VII.— THE  NITROGEN  GROUP 125 

"       VIII.— BORON 160 

"          IX.— THE  CARBON  GROUP         .        .       .       e       .163 

"            X. — THE  ELECTRO-POSITIVE  ELEMENTS  .        .        .  185 

"          XL— THE  ALKALI  METALS                                      .  193 

XII.— THE  DYAD  METALS 213 

"       XHI.-THE  TRIAD  METALS 242 

"       XIV.— THE  TETRAD  METALS 245 

"         XV.— THE  HEXAD  METALS 249 

"       XVL— KERAMICS  AND  GLASS       .        .        .        .        .  280 

(v) 


vi  CONTENTS. 

ORGANIC  CHEMISTRY. 

PAGE 

CHAPTEK  XVII.— THE  COMPOUNDS  OF  CARBON   .        .  .285 

"            XVIII.— THE  CYANOGEN  COMPOUNDS    .  •     .  .305 

"                XIX.— THE  HYDROCARBONS         .        .        .  .315 

XX— THE  ALCOHOLS  .        .        .        .        .  .320 

"                XXI.— THE  CARBOHYDRATES       .        .        .  .336 

"              XXII.— ALDEHYDES  AND  KETONES       .        .  .346 

XXIII.— ORGANIC  ACIDS .354 

"             XXIV.— AMIDES  AND  AMINES        .        .        .  .377 

XXV.— THE  ETHERS 392 

XXVI.— THE  AROMATIC  HYDROCARBONS      .  .    409 

XXVII.— SUBSTANCES  CONTAINING  O  AND  OH  .    425 

XXVIII. — SUBSTANCES  CONTAINING  NITROGEN  .    449 

XXIX. — VEGETABLE  AND  ANIMAL  CHEMISTRY  .    470 

APPENDIX. 

CRYSTALLOGRAPHY 483 

PROBLEMS 485 

INDEX    .        .  .    491 


CHEMISTRY. 


CHAPTEE    I. 

LAWS    OF    CHEMICAL    COMBINATION. 

1.  Many  common  phenomena  are  the  results  of  chemical 
action.     If  iron  filings  are  moistened  and  exposed  to  the 
air,  they  become  changed  to  the  orange-red  powder  called 
iron  rust.     The  iron  loses  its  luster,  its  tenacity,  its  prop- 
erty of  being  attracted  by  a  magnet;  in  fact,  it  loses  its 
identity,  and  we  recognize   iron   rust  as  a  different  kind 
of  matter  from  iron.     When  a  body  is  so  altered  that  its 
physical  properties  disappear,  and  a  new  kind  of  matter 
has  been  formed,  a  chemical  action  has  taken  place. 

The  constituents  of  the  atmosphere  are  continually 
acting  upon  the  substances  which  are  found  on  the  sur- 
face of  the  earth,  and  are  effecting  in  them  chemical 
changes.  Among  these  changes  are  the  decay  of  leaves, 
the  burning  of  wood  and  candles,  the  rusting  of  iron, 
and  the  souring  of  milk  and  cider.  As  the  result  of  these 
actions  new  bodies  are  formed,  which  are  essentially 
different  from  the  original  substances. 

2.  The    atmosphere    is  so  constantly  engaged  in  pro- 
ducing   chemical    changes  that    we   must  first   determine 
what  its  constituents  are. 

Experiment  1. — Place  in  a  glass  beaker  a  freezing  mixture  of 
ice  and  salt.  After  a  little,  the  outside  of  the  dish  will  be  covered 
with  moisture,  which  in  process  of  time  will  collect  in  drops  of 
water.  See  Exp.  39. 

(7) 


CHEMISTRY. 


The  atmosphere,  therefore,  contains  water  which  is 
usually  disseminated  through  it  as  an  invisible  vapor. 
The  quantity  of  aqueous  vapor  in  the  air  is  always 
small,  and  of  no  constant  proportions.  The  average  is 
1.4  per  cent  by  volume,  or  0.87  per  cent  by  weight. 

The  vapor  of  water  may  be  removed  from  air  and 
other  gases  by  passing  them  through  vessels  containing 
calcium  chloride  or  sulphuric  acid  or  quicklime. 

Exp.  2.  —  Expose  a  lump  of  quicklime  in  an  open  dish.  After 
a  few  days  it  will  crumble  to  a  light  powder.  This  is  air-slaked 
lime.  The  lime  has  combined  with  the  water  in  the  air  and  has 
formed  a  compound  which  is  called  calcium  hydrate. 

After  a  longer  exposure  the  lime  will  combine  with 
another  constituent  of  the  air  called  carbonic  acid,  or 
carbonic  anhydride,  to  form  calcium  carbonate.  If  old 
mortar  be  dropped  in  a  dilute  acid,  it  will  effervesce  or 
give  off  bubbles  of  the  same  gas,  which  has  been  obtained 
by  long  contact  with  the  air.  Carbonic  anhydride  forms 
usually  four  parts  in  10000  of  the  atmosphere,  but  even  this 

relatively  small  quantity  is 
essential  to  the  growth  of 
plants. 

Free  carbonic  anhydride 
may  be  removed  from  air  or 
other  gases  by  passing  them 
through  a  solution  of  potas- 
sium hydrate,  or  through 
"milk  of  lime." 

Exp.  3.  —  Invert  a  glass  tube 
FIG.  l.  closed  at  one  end  and  filled  with 

dry   air   in    a    basin    containing 

mercury.  "Wrap  a  piece  of  clean  sodium  in  filter  paper,  and  bring 
this  within  the  tube.  After  a  few  days  the  volume  of  the  air  will 
contract,  and  the  mercury  will  rise  and  fill  about  one-fifth  of  the 
tube.  Now,  close  the  tube  with  the  thumb,  and  remove  it  from  the 
basin.  Test  the  gas  remaining  by  plunging  an  ignited  splinter  of 
pine  within  the  tube.  The  blaze  will  instantly  be  extinguished. 


THE  ATMOSPHERE.  9 

The  gas  that  remains,  and  that  will  not  support  com- 
bustion, is  called  nitrogen.  It  constitutes  79.19  per  cent 
of  dry  air  by  volume,  or  76.86  per  cent  by  weight. 

The  constituent  of  the  air  which  has  been  removed,  is 
called  oxygen.  It  constitutes  20.81  per  cent  by  volume,  or 
23.14  per  cent  by  weight  of  dry  air.  Open  the  paper  in 
which  the  sodium  was  wrapped.  The  metal  will  be  seen 
to  be  coated  with  a  dry  powder,  which  is  called  sodium 
oxide  (Na2O).  It  has  also  gained  in  weight.* 

Oxygen  is  the  efficient  agent  in  producing  the  changes 
mentioned  in  §  1.  The  nitrogen  is  inert,  and  its  principal 
use  seems  to  be  to  dilute  the  oxygen  and  diminish  the 
rapidity  of  its  action.  When  a  metal  corrodes  or  rusts 
in  the  air,  it  does  so  by  combining  \vith  oxygen.  The 
process  is  called  oxidation,  and  the  product  formed  by 
oxidizing  a  metal  is  called  an  oxide  of  that  metal. 

The  air  contains  also  very  small  traces  of  ammonia 
and  other  vapors,  but  these  may  be  neglected  for  the 
present.  All  these  constituents  of  the  air  are  merely 
mixed  together  and  are  therefore  readily  separated. 
Water,  for  instance,  will  absorb  from  the  air  a  greater 
proportion  of  oxygen  than  of  nitrogen ;  so  that  the  air 
which  fishes  breathe  is  richer  in 
oxygen  than  that  which  we 
breathe. 

The  principal  constituents  of 
the  atmosphere  are  water,  car- 
bonic anhydride,  nitrogen,  and 
oxygen. 

3.  We  must  also  determine 
the  constituents  of  water,  be- 
cause it  is  an  efficient  agent  in 
producing  chemical  changes.  FlG-  2- 

Exp.  4. — Fill  a  stout  test  tube  with  water  and  invert  this  in  a 
dish  of  water.  Pass  into  the  mouth  of  the  tube  a  small  pellet  of 

*If  the  teacher  has  no  mercurial  cistern,  he  may  remove  the  oxygen  by 
phosphorus,  or,  better,  by  potassium  pyrogallate  (see  Exp.  78). 


10  CHEMISTRY. 

sodium  wrapped  in  filter  paper.  Bubbles  of  gas  instantly  rise  to  the 
top  of  the  tube  and  force  the  water  out.  Remove  the  tube  from  the 
water,  and  apply  a  lighted  splinter  to  its  mouth.  The  gas  burns 
with  a  pale  flame. 

This  gas  is  called  hydrogen,  and  constitutes  ^  of  the 
weight  of  water.  Test  the  water  of  the  dish  by  reddened 
litmus  paper ;  it  will  become  blue.  Moisten  another  lit- 
mus paper,  and  put  a  little  of  the  sodium  oxide,  obtained 
by  Exp.  3,  on  it ;  the  same  change  of  color  will  be  pro- 
duced, because  sodium  oxide  has  also  been  formed  by 
the  decomposition  of  the  water. 

Water,  then,  is  composed  of  hydrogen  and  oxygen. 
"When  sodium  oxide  dissolves  in  water,  it  forms  sodium 
hydrate,  or  the  caustic  soda  of  the  apothecary  (Na2O, 
H20,  or  2NaHO). 

Exp.  5. — Boil  a  few  leaves  of  red  cabbage  in  water,  and  decant 
the  clear,  purplish  liquor.  Caustic  soda  dropped  in  this  infusion 
changes  it  to  a  green  color. 

Bodies  which  are  capable  of  changing  such  vegetable 
blues  to  green  are  called,  in  ordinary  language,  alkalies. 
The  common  alkalies  are  soda,  potassa,  and  ammonia. 
They  have  an  acrid  taste  and  a  soapy  feel. 

Exp.  6.— Prepare  chlorine  water  as  directed  in  £  122.  A  little 
of  this  dropped  in  the  cabbage  infusion,  or  on  litmus  paper,  will 
instantly  decolorize  or  bleach  it. 

Exp.  7. — Fill  a  flask  completely  with  chlorine  water,  invert  it 
in  a  cup  of  water,  and  expose  it  for  some  days  to  the  sunlight. 
Bubbles  of  gas  will  collect  in  the  upper  part  of  the  flask,  and  the 
odor  of  the  chlorine  and  its  bleaching  power  will  entirely  disappear 
if  it  is  exposed  long  enough. 

Exp.  8. — Light  a  splinter  of  pine,  and  blow  out  the  flame  so 
as  to  leave  only  a  glowing  coal.  Plunge  this  into  the  gas  of  the 
flask:  it  will  instantly  be  re-lighted,  and  burn  brightly. 

This  gas  supports  combustion,  and  is  called  oxygen. 
It  constitutes  |-  of  the  weight  of  water.  The  chlorine 
has  also  decomposed  the  water;  but,  unlike  sodium,  it 


WATER.  11 

liberates  oxygen  and  combines  with  the  hydrogen.  The 
compound  formed  is  called  hydrogen  chloride,  or,  more 
frequently,  hydrochloric  acid  (HC1). 

Test  the  water  in  the  cup  with  the  cabbage  infusion 
or  with  blue  litmus  paper.  It  will  be  reddened'*  and 
the  water  will  have  a  sour  taste 

Bodies  which  change  vegetfrole  blues  to  red  are  called, 
in  ordinary  language,  acids.  The  common  acids  have  a 
sour  taste. 

These  experiments  show  that  water  contains  oxygen 
and  hydrogen.  The  following  experiment  shows  that  it 
contains  only  these  gases. 

Exp.  9. — Prepare  hydrogen  as  directed  in  §  82 ;  dry  it  by 
passing  the  gas  through  a  tube  filled  with  calcium  chloride,  and 
attach  to  this  a  delivery  tube  drawn  out  to  a 
fine  orifice.  After  all  the  air  has  been  expelled 
from  the  apparatus,!  light  the  hydrogen,  and 
hold  over  the  flame  a  cold  bell  glass  (Fig.  3). 
The  hydrogen  burns  because  it  unites  with  the 
oxygen  of  the  air,  and  the  product  of  the  com- 
bustion collects  in  drops  on  the  inside  of  the 
bell  glass.  (See  §§  46  and  47). 

It  is  water  (H2O).  Two  parts,  by 
weight,  of  hydrogen  unite  with  sixteen 
parts,  by  weight,  of  oxygen  to  form 
eighteen  parts  of  water.  Thus,  eight 
ounces  of  oxygen  are  required  to  burn 
one  ounce  of  hydrogen  to  form  nine 
ounces  of  water.  These  last  quantities 
are  evidently  in  the  same  proportions 
as  those  first  given  ;  or,  2  :  16  ::  1  :  8. 

These  proportions  are  always  the  same.  Because  they 
are  constant,  and  because  the  constituents  can  not  be 
separated  from  each  other  by  merely  physical  means, 
we  say  that  water  is  a  true  chemical  compound. 

*  If  all  the  odor  of  the  chlorine  has  not  disappeared,  it  will  also  be  more 
or  less  bleached. 

t  Hydrogen  mixed  with  air  is  dangerously  explosive. 


12 


CHEMISTRY. 


The  aqueous  vapor  in  the  atmosphere  promotes  many 
chemical  changes :  thus,  iron  and  wood  will  remain  un- 
changed for  years  in  dry  air ;  but  in  moist  air,  the  iron 
readily  rusts  and  the  wood  decays.  The  oxygen  which 
causes  the  oxidizing  of  metals  and  the  decay  of  vegeta- 
ble matter  is  obtained  by  the  decomposition  of  water. 

4.  Chemistry  treats  of  the  composition  of  bodies,  and 
of  those    changes    in    matter   by   which   the    substances 
acted  upon  suffer  a  loss  of  identity. 

The  chemist  endeavors  to  determine  the  composition  of  bodies 
by  subjecting  them  to  various  experiments,  which  are  designed  to 
effect  essential  changes  in  their  structure.  By  many  such  it  has 
been  found  that  a  limited  number  of  substances  consist  of  a  single 
uniform  kind  of  matter  —  as,  sodium,  oxygen,  hydrogen;  and  that 
by  far  the  greater  number  of  substances  are  composed  of  two  or 
more  constituents  —  as,  water,  sodium  oxide,  sodium  hydrate. 

5.  Bodies   which    have   been    made   to   yield   but   one 
kind  of  matter  are  called  simple  substances  or  elements. 

Bodies  which  may  be  separated  into  two  or  more 
elements  are  called  compound  substances. 

The  known  elements  are  sixty-five  in  number.  There 
can  be  no  doubt  that  others  will  be  discovered ;  and  it 
is  possible  that  some  substances  which  are  now  consid- 
ered simple  will  hereafter  be  found  to  be  compound. 

TABLE   OF   THE   ELEMENTS. 
I.    THE  NON-METALS— 13. 


FLUORINE 

F 

CHLORINE 

Cl 

BROMINE 

Br 

IODINE 

I 

OXYGEN 

O 

SULPHUR 

s 

Selenium 

Se 

Tellurium 

Te 

roMic 

2IGHT. 

ELEMENT. 

8YM] 

19. 

Boron 

B 

35.5 

80. 

CARBON 

C 

127. 

SILICON 

Si 

16. 

NITROGEN 

N 

32. 

PHOSPHORUS 

P 

79.4 

128. 

ATOMIC 
WEIGHT. 

11. 


12. 

28. 

14. 
31. 


THE  ELEMENTS. 


13 


II.   THE  SEMI-METALS  — 


ELEMENT. 

SYMBOL. 

ATOMIC 
'     WEIGHT. 

ELEMENT. 

SYMBOL. 

ATOMIC 
WEIGHT. 

Vanadium 

V 

51.3 

Titanium 

Ti 

50. 

ARSENIC 

As 

75. 

Zirconium 

Zr 

89.6 

Niobium 

Nbor 

Cb     94. 

TIN 

Sn 

118. 

Antimony 

Sb 

122. 

Tantalum 

Ta 

182. 

Molybdenum 

Mo 

92. 

Bismuth 

Bi 

210. 

Tungsten 

W 

184. 

Uranium 

U 

120. 

HYDROGEN  H        1. 

III 

.   THE  METALS  —  39. 

Lithium 

Li 

7. 

Cerium 

Ce 

92. 

SODIUM 

Na 

23. 

Lanthanum 

La 

92.8 

POTASSIUM 

K 

39.1 

Rubidium 

Rb 

85.4 

Thallium 

Tl 

203.6 

Caesium 

Cs 

133. 

LEAD 

Pb 

207. 

Thorium 

Th 

231. 

SILVER 

Ag 

108. 

Chromium 

Cr 

52.4 

Glucinum 

Glor 

Be        9.4 

Manganese 

Mn 

55. 

MAGNESIUM 

Mg 

24. 

IRON 

Fe 

56. 

ZINC 

Zn 

65. 

Cobalt 

Co 

59. 

Cadmium 

Cd 

112. 

Nickel 

Ni 

59. 

CALCIUM 

Ca 

40. 

GOLD 

Au 

197. 

Strontium 

Sr 

87.5 

Barium 

Ba 

137. 

Ruthenium 

Ru 

104.4 

Osmium 

Os 

199.2 

COPPER 

Cu 

63.5 

MERCURY 

Hg 

200. 

Palladium 

Pd 

106.6 

PLATINUM 

Pt 

197.4 

ALUMINIUM 

Al 

27.5 

Rhodium 

Rh 

104.4 

Gallium 

Ga 

69.9 

Iridium 

Ir 

198. 

Indium 

In 

113.4 

Yttrium 

Y 

61.7 

Davyum 

Da 

150? 

Didymium 

Di 

96. 

Erbium 

Er 

112.6 

NOTE.— The  atomic  weights  are  those  given  in  the  "Neues  Handwoerterbuch 
der  Chemie."    Other  classifications  are  given  on  pp.  59,  60, 192. 


14  CHEMISTRY. 

The  symbol  placed  after  each  element  is  the  abbreviation  of  its 
Latin  name;  thus,  H  stands  for  hydrogen;  Ag  for  silver  (Argentum); 
Hg  for  mercury  (Hydrargyrum);  Fe  for  iron  (Ferrum).  These  sym- 
bols are  so  convenient  that  the  student  should  at  once  familiarize 
himself  with  those  of  the  most  common,  the  names  of  which  in  the 
table  are  printed  in  capitals. 

6.  The    study   of    Chemistry    is    much    facilitated    by 
classifying  the  elements  in  groups,  whose  members  have 
many  characteristics  in   common.     But   it   is   impossible 
to   draw  any  strict   dividing   line;    and   hence   all   such 
groupings   must   be   regarded   as   made   merely  for  the 
sake   of  convenience,  and   liable  to  be  varied  hereafter. 
It    will    be    noticed    that    three    principal    groups    are 
given  :  the  non-metals,  the  semi-metals,  and  the  metals. 
No    definition    has    been    given    which    sharply    distin- 
guishes  them ;    but   it   may  be   generally   observed,  (1) 
That   the    metals   are    good    conductors   of  heat  and   of 
electricity,  and  are  characterized  by  a  peculiar    metallic 
luster;    (2)  The   non-metals   are   non-conductors  of  heat 
and  of  electricity ;    (3)   The   metals  are   electro-positive 
elements,  and  the  non-metals  electro-negative.     By  this 
we  mean  that  when   their   compounds  are   decomposed 
by  the  galvanic  current,  the  metals   tend   to   collect  at 
the   negative   pole   of  the   battery,  and   the   non-metals 
at    the    electro-positive   pole.*    (4)    Generally,    the    non- 
metals   form,  with    oxygen,  acid  anhydrides,  while  the 
metals    form    basic    anhydrides,    as    will    be    explained 
hereafter.     (5)  The   semi-metals  are  elements  which  re- 
semble the  metals  in  their  physical  properties,  and   the 
non-metals   in    their   chemical    properties ;    that  is,  they 
have    the    luster    of  the    metals,    but   their    oxides    are 
most  frequently  acid  anhydrides. 

7.  The  most  important  processes  employed  in  chemistry 
are  readily  illustrated  by  a  few  experiments,  which  the 
student  is  earnestly  requested  to  repeat  for  himself. 

*See  §  48. 


COMBINATION.  15 


I. — COMBINATION. 

Exp.  10. — Cut  off  a  thin  slice  of  phosphorus,  and,  having  dried 
it  between  two  folds  of  filter  paper,  lay  it  on  a  dry  plate.  Now 
put  upon  this  a  flake  of  iodine.  The  two  elements  unite  and  evolve 
so  much  heat  that  a  portion  of  the  phosphorus  combines  also  with 
the  oxygen  of  the  air,  and  burns  brightly.  White  fumes  are  given 
off,  which  are  a  compound  of  phosphorus  and  oxygen,  called  phos- 
phorus pentoxide.  The  red  solid  that  remains  on  the  plate  is 
called  phosphorus  iodide. 

Exp.  11. — Rub  together  in  a  mortar  a  small  globule  of  mercury 
with  a  little  more  than  five-fourths  of  its  weight  of  iodine,  moist- 
ened with  a  few  drops  of  alcohol.  The  mercury  and  iodine  unite 
to  form  a  scarlet  powder,  which  is  called  mercuric  iodide. 

Exp.  12. — Place  a  bright  strip  of  zinc  in  a  small  dish,  and 
cover  it  with  water.  Now  drop  on  the  zinc  a  few  flakes  of  iodine. 
After  a  few  hours  the  iodine  will  disappear  in  the  liquid.  It  has 
united  with  a  portion  of  the  zinc  to  form  zinc  iodide.  The  combi- 
nation may  be  accelerated  by  frequent  stirring,  and  by  gently 
warming  the  mixture. 

If,  now,  the  remaining  zinc  be  removed,  tha  zinc  iodide  may  be 
obtained  by  evaporating  the  liquid  on  a  water  bath. 

Exp.  13. — Prepare  a  strong  solution  of  chlorine  water,  as  di- 
rected in  §  122.  Put  some  of  this  in  a  glass  vial,  with  a  very  small 
globule  of  mercury,  and  shake  frequently.  After  a  time  the  mer- 
cury will  disappear,  and  most  of  the  odor  of  the  chlorine;  the 
chlorine  will  unite  with  the  mercury  to  form  mercuric  chloride. 

This  body  may  be  obtained  by  evaporating  the  liquid,  or  the 
solution  may  be  used  in  the  experiments  which  follow. 

8.  These  experiments  show  that  two  bodies  may  com- 
bine directly. 

The  process  of  uniting  two  bodies  to  form  a  chemical 
compound  is  called  synthesis.  When  only  two  elements 
enter  into  combination,  the  product  is  called  a  binary 
compound.  Such  compounds  are  named  by  affixing  the 
termination  ide  to  the  non-metallic,  or  electro-negative, 
element,  and  prefixing  the  name  of  the  metal,  or  the 
electro-positive  element ;  as,  zinc  iodide,  mercuric  iodide. 


16 


CHEMISTRY. 


In  this  way  we  may  name  the  oxides,  chlorides, 
iodides,  phosphides,  etc. ;  but  it  is  important  to  note 
that  the  termination  ide  is  never  used  except  with 
binary  compounds. 

9.  The  foregoing  experiments  show  that  chemical 
changes  are  marked  by  alterations  in  color,  taste,  odor, 
form,  and  sometimes  by  the  development  of  heat  and 
light.  The  compounds  formed  are  essentially  different 
from  the  elements  that  enter  into  combination.  On  the 
other  hand,  if  bodies  are  merely  mixed  together,  no 
such  changes  occur. 

Exp.  14. — Kub  together  in  a  mortar  56  parts  of  iron  filings  and 
32  of  sulphur.  Divide  the  mixture  into  four  equal  portions.  From 
the  first  portion  the  iron  may  be  removed  by  a  magnet;  from  the 
second  portion  the  sulphur  may  be  re- 
moved by  dissolving  it  in  carbonic  di- 
sulphide; and  from  the  third,  by  direct- 
ing upon  it  a  gentle  stream  of  water, 
which  will  suffice  to  wash  away  the 
lighter  particles  of  the  sulphur,  and 
leave  the  heavier  iron  behind.  Now 
heat  the  fourth  portion  in  a  test  tube. 
The  sulphur  aad  iron  combine  to  form 
ferrous  sulphide,  which  is  a  true  chemical 
compound  whose  constituents  are  in- 
separable by  mechanical  means. 

Further,    a    mixture    may    be 
^       made   in   all   conceivable   propor- 
FIG.  4.  tions.     This  is  not  the  case  in  a 

chemical    combination.     In    Exp. 

12,  a  portion  of  the  zinc  was  not  acted  upon.  If  in 
Exp.  11  we  employ  too  much  iodine,  the  excess  will 
remain  uncombined  and  mixed  with  the  mercuric  iodide. 
In  the  last  example,  if  an  excess  of  sulphur  is  used,  it 
may  be  dissolved  by  carbonic  disulphide,  after  first  pul- 
verizing the  product. 


CONSTANT  PROPORTIONS.  17 

10.  Law  of  constant  proportions. — In  every  chemical 
compound,  the  proportions  of  the  elements  united  are  always 
fixed,  definite,  and  invariable. 

Thus  the  following  named  binary  compounds  are  al- 
ways found  to  contain : 

Sodium  chloride,  23  parts  of  sodium,  35.5  parts  of  chlorine. 

Sodium  iodide,  23         "         sodium,  127          "  iodine. 

Potassium  chloride,  39         "         potassium,  35.5         "  chlorine. 

Potassium  iodide,  39         "         potassium,  127          "  iodine. 

Zinc  iodide,  65        "         zinc,  254         "  iodine. 

Zinc  chloride,  65         "         zinc,  71          "  chlorine. 

These  are  the  only  binary  compounds  of  iodine  and 
chlorine  with  sodium,  potassium,  and  zinc.  Iodine  and 
chlorine,  however,  combine  with  some  of  the  elements 
to  form  two  or  more  distinct  compounds;  but  for  the 
same  compound,  the  proportions  are  always  constant. 

Exp.  15.— Repeat  Exp.  11,  using  only  five-eighths  as  much 
iodine  as  mercury.  A  greenish-yellow  powder  will  be  produced, 
containing  twice  the  proportional  quantity  of  mercury.  It  is  called 
mercurous  iodide  (Hgl,  or  Hg2I2). 

If  a  quantity  of  iodine  intermediate  between  five- 
fourths  and  five-eighths  its  weight  of  mercury  be  used, 
both  iodides  will  be  produced  and  remain  mixed  to- 
gether. Strong  alcohol  will  dissolve  out  of  the  mixture 
the  mercuric  iodide,  and  leave  the  mercurous  iodide 
behind. 

Mercury,  therefore,  forms  two  compounds  with  iodine : 
200  parts  of  mercury  may  combine  with  127  parts  of 
iodine  to  form  mercurous  iodide,  or  with  254  parts  of 
iodine  to  form  mercuric  iodide.  The  proportion  of 
iodine  in  the  second  is  exactly  twice  that  of  the  first. 
We  distinguish  between  two  such  compounds  by  the 
terminations  ic  and  ous  added  to  the  more  positive  ele- 
ment :  the  ic  denoting  the  higher  degree  of  combination  ; 
the  ous,  the  lower. 

Chem.— 2. 


18  CHEMISTRY. 

Exp.  16. — Boil  a  solution  of  mercuric  chloride  with  a  globule 
of  metallic  mercury.  A  white  powder  will  separate  from  the  mix- 
ture. This  is  mercurous  chloride  (HgCl,  or  Hg2Cl2). 

The  proportion  of  chlorine  in  the  mercuric  chloride 
is  twice  that  in  the  mercurous  chloride.  Some  such 
simple  relation  is  generally  found  when  two  elements 
form  more  than  one  compound.  Hence: 

11,  The  Law  of  multiple  proportions.  —  When  one  body 
is  capable  of  uniting  with  another  body  in  several  propor- 
tions, these  proportions  bear  a  simple  relation  to  each  other. 

Thus,  an  element,  A,  may  unite  with  another  element, 
B,  to  form  compounds,  which  may  be  represented  by 

A-J-B,    A  +  2B,    A  +  3B,    A  +  4B,    A  +  5B, 
2A  -f-  3B,    2A  +  5B,    2A  +  7B,  etc.,  etc. 

We  have  an  excellent  illustration  of  this  law  in  the 
compounds  of  nitrogen  and  oxygen.  These  are  five  in 
number : 

PARTS  IN  100  BY  WEIGHT.     RATIOS. 


>T. 

o. 

N. 

o. 

SYMBOLS. 

Nitrous  oxide, 

63.64 

:  36.86 

::  28  : 

16 

N 

2° 

Nitric  oxide, 

46.67 

:  53.33 

::  28  : 

32 

N 

202 

Nitrous  anhydride, 

36.85 

:  63.15 

::  28  : 

48 

N 

2°3 

Nitric  peroxide, 

30.44 

:  69.56 

::   28  : 

64 

N 

2o4 

Nitric  anhydride, 

25.93 

:  74.07 

::   28  : 

80 

N 

2O5 

This  shows  that  28  parts  of  nitrogen  may  combine  to 
form  a  series  of  compounds  with  oxygen,  containing 
one,  two,  three,  four,  and  five  times  16  parts  of  oxygen. 
When  a  scries  of  binary  compounds  is  formed  of  two  ele- 
ments, we  may  distinguish  between  them  by  the  prefixes 
mono  or  prot  =  onQ;  bi,  dent,  or  di  =  iwo-,  tri  or  ter  — 
three;  sesqui  —  two  to  three;  te£ra  =  four;  penta,  five,  etc., 
affixed  to  the  element  that  increases  by  multiples.  Some- 
times, also,  the  names  of  the  elements  are  separated  by 
of:  thus  the  last  series  may  be  severally  named  protoxide, 
dioxide,  trioxide,  tctroxide,  and  pentoxide  of  nitrogen. 


LAWS  OF  COMBINATION.  19 

Many  compounds  have  two  or  more  names :  one  the 
vulgar  name,  others  derived  from  former  theories  of 
chemists,  and  still  others  in  modern  use.  Thus  the  two 
chlorides  of  mercury  have  each  a  half  a  dozen  names, 
the  following  of  which  are  still  allowable : 

Formula,  Hg2Cl2,  or  HgCl.  HgCl2. 

Vulgar  name,  Calomel.  Corrosive  Sublimate. 

Old  name,  Protochloride  of  Mercury.  Bichloride  of  Mercury. 

New  name,  Mercurous  Chloride.  Mercuric  Chloride. 

12,  It  follows  naturally,  from  the  laws  of  constant 
and  multiple  proportions,  that  the  weights  in  which 
bodies  unite  may  be  represented  by  numbers.  We  also 
find  that  the  same  number,  or  a  multiple  of  it,  will 
represent  the  proportion,  by  weight,  in  which  any  ele- 
ment will  combine  with  any  other  element.  Thus  iodine 
may  always  be  represented  by  127,  or  by  some  multiple 
of  it.  The  numbers  thus  found  are  called  the  combining 
numbers  of  the  elements. 

Law  of  combining  proportions. — Every  element  in  com- 
bining with  other  elements  does  so  in  a  fixed  proportion, 
which  may  be  represented  numerically. 

The  numbers  given  on  pp.  12  and  13  are  the  combining 
proportions  in  which  each  element  unites  with  the  other 
elements.  Further,  it  has  been  agreed  that  each  symbol 
shall  not  only  be  an  abbreviation  of  the  name  of  an 
element,  but  also  represent  one  combining  number.  Hg, 
therefore,  represents  200  parts  of  mercury  by  weight; 
I,  127  parts  of  iodine ;  O,  16  parts  of  oxygen,  etc.  A 
number  placed  below  a  symbol  represents  how  many 
multiples  of  the  element  are  taken  :  thus,  I2  represents 
two  combining  proportions,  or  254  parts,  of  iodine.  We 
may  then  represent  mercurous  iodide  by  Hgl,  or  by 
Hg2I2,  and  mercuric  iodide  by  HgI2.  If  we  desire  to 
represent  a  multiple  of  a  compound,  we  do  so  by  placing 
a  numeral  before  the  symbol  of  the  compound;  thus, 


20  CHEMISTRY. 

2Hg2I2  represents  two  proportions  of  mercurous  iodide; 
2HgI2,  two  proportions  of  mercuric  iodide.  The  num- 
ber, when  placed  before  a  compound,  multiplies  each 
element  in  the  compound  by  itself.  The  same  thing 
is  sometimes  done  more  conveniently  by  inclosing  the 
symbols  within  parentheses,  and  placing  the  numeral 
either  before  or  below  the  parenthetical  marks ;  for 
example,  2TIgI2,  2(IIgI2),  (HgI2)2,  represent  the  same 
quantities. 

13.  Binary   compounds   may   also   unite    and   produce 
other  compounds. 

Exp.  17. — Quicklime  (CaO)  and  water  (H2O)  are  binary  com- 
pounds. Put  a  large  lump  of  quicklime  on  a  plate,  and  pour  on 
it  a  small  quantity  of  water.  The  two  binaries  unite;  the  lime 
becomes  heated  and  crumbles  away  to  a  light  powder,  which  is 
called  slaked  lime.  Its  composition  may  be  represented  by  CaO, 
H20,  or  CaH202,  or  Ca(OH)2. 

Exp.  18. — Place  a  piece  of  clean  sodium  in  a  bottle  filled  with 
dry  air  or  oxygen.  The  sodium  changes  to  sodium  oxide  (Na2O). 
Now  bring  into  the  flask  a  stream  of  carbonic  anhydride  (CO2).  * 
The  two  binary  compounds  unite  to  form  sodium  carbonate  (Na2O, 
CO2,  or  Na2CO3). 

When  two  binary  compounds  unite,  the  product  con- 
tains three  elements,  and  is  called  a  ternary  compound. 
Thus,  sodium  carbonate  contains  three  elements,  Na,  C, 
and  O. 

A  few  compounds  are  formed  by  the  union  of  two 
ternaries.  These  usually  contain  four  elements,  and  are 
called  double  salts.  Common  alum  is  an  example:  it 
consists  of  potassium  sulphate  and  aluminium  sulphate ; 
besides  which  it  contains  water,  which  is  called  water 
of  crystallization.  The  entire  formula  of  alum  is  K2O, 
SO3+A12O3,  3SO3-j-24H2O,  or  K  Al  2SO4  +  12H2O. 

14.  Compounds  may  also  be  formed  indirectly. 


*  The  directions  for  the  preparation  of  this  are  on  page  171. 


SUBSTITUTION.  21 


II.  —  SUBSTITUTION. 

Exp.  19. — Put  a  little  mercuric  iodide  in  a  vial  half  filled  with 
water.  Add  a  few  drops  of  saturated  chlorine  water,  and  shake 
the  mixture.  A  part  of  the  iodine  is  set  free  and  darkens  the 
liquid.  The  mercury  is  not  seen,  because  it  has  combined  with  the 
chlorine  to  form  mercuric  chloride,  and  is  dissolved.  The  odor  of 
the  chlorine  also  disappears. 

The  whole  of  the  iodine  may  be  displaced  by  the  chlorine,  by 
adding  the  chlorine  water  in  small  quantities,  and  shaking  the 
mixture  after  each  addition.  The  free  iodine  may  be  separated 
from  the  mixture  by  adding  a  teaspoonful  of  chloroform  to  the  water, 
and  shaking.  The  chloroform  dissolves  the  iodine  and  settles  to 
the  bottom.  The  supernatant  liquid  may  then  be  poured  off,  and 
the  mercuric  chloride  be  obtained  by  evaporation. 

Exp.  20. — Mercurous  iodide,  treated  in  the  same  way,  yields 
mercurous  chloride /and  free  iodine. 

Exp.  21. — Put  another  portion  of  mercuric  iodide  in  a  small 
beaker  with  a  little  water.  Place  in  this  a  clean  zinc  strip,  and 
warm  gently.  In  a  few  hours  the  mercuric  iodide  will  entirely  dis- 
appear, and  a  coating  of  mercury  will  be  seen  on  the  zinc.  In 
this  case  the  zinc  has  displaced  the  mercury  in  the  compound,  and 
has  formed  zinc  iodide,  which  remains  in  the  solution.  It  may 
also  be  obtained  by  filtering  arid  evaporating  the  liquid. 

15.  These  experiments  show  that  we  may  form  new 
compounds  by  displacing  one  element  by  another.  The 
process  of  forming  a  new  compound  by  displacement  is 
called  substitution. 

III. — METATHESIS. 

Exp.  22. — Pour  into  a  test  tube  a  solution  of  mercuric  chloride, 
and  add  to  this,  drop  by  drop,  a  solution  of  zinc  iodide.  The  ele- 
ments of  the  two  compounds  will  be  rearranged  to  form  two  new 
compounds, — solid,  red,  mercuric  iodide  and  zinc  chloride.  * 

*The  student  will  notice  that  the  red  powder,  which  is  at  first  formed,  imme- 
diately disappears,  because  an  excess  of  mercuric  chloride  dissolves  it:  that  it 
then  settles  to  the  bottom  of  the  tube,  or  precipitates;  and,  finally,  if  more  zinc 
iodide  is  added,  and  the  mixture  shaken,  it  again  disappears,  because  an  excess 
of  zinc  iodide  dissolves  it.  The  example  shows  the  importance  of  avoiding 
excess  in  chemical  manipulations.  A  drop  too  much  is  excess. 


CHEMISTRY. 


If  the  mercuric  iodide  be  filtered  off,  the  zinc  chloride, 
which  remains  dissolved,  may  be  obtained  by  evaporating 
the  solution  to  dryness. 

Exp.  23.— Provide  a  small  flask,  as  shown  in  Fig.  5,  with  a 
cork  through  which  passes  a  long  funnel  tuhe,  A,  reaching  nearly 
to  the  hottom  of  the  flask;  also  a  shorter  tube,  B,  bent  at  right 
angles,  and  just  passing  through  the  cork.  Make  all  the  fittings 

air-tight.  Now  put  some  ferrous  sul- 
phide in  the  flask,  and  insert  the 
cork.  Pour  through  the  funnel  tube 
a  little  hydrochloric  acid.  Chemical 
action  will  immediately  begin,  and 
an  extremely  offensive  gas,  hydrogen 
sulphide,  will  be  given  off. 

Hydrochloric  acid  is  a  solution 
of  hydrogen  chloride.  When  this  is 
poured  on  ferrous  sulphide,  the  ele- 
ments are  arranged  into  two  new 
compounds,  —  ferrous  chloride  and 
hydrogen  sulphide. 

Exp.  24. — Having  previously  at- 
tached, by  a  rubber  tube,  the  glass 
tube,  C,  to  the  flask,  pass  the  escaping 
hydrogen  sulphide  into  any  of  the 
compounds  of  mercury  previously 

obtained.  They  will  all  blacken  from  the  formation  of  mercurous 
sulphide,  or  mercuric  sulphide,  and  the  hydrogen  will  enter  into 
combination  with  the  iodine  or  with  the  chlorine. 

16.  These  experiments  show  that  new  compounds  may 
be  formed  by  an  interchange  of  the  elements  previously 
existing  in  other  compounds. 

The  process  of  forming  new  bodies  by  an  interchange 
of  the  elements  of  two  compounds  is  called  double  de- 
composition, or  metathesis. 

17.  Chemical  changes  like  those  already  described  are 
called  reactions;  the  bodies  which  take  part  in  them  are 
called  reagents.     We  may  represent  reactions  by  equations 
not    unlike    those    of  algebra.      The  sign  -j-  represents 


FIG.  5. 


DOUBLE  DECOMPOSITION.  23 

added  to,  or  and  ;   the  sign  —  ,  taken  from  ;   the  sign  =, 
produces,  or  results  in.     Thus,  the  formula, 


means  "  zinc  iodide  added  to  mercuric  chloride,  produces 
mercuric  iodide  and  zinc  chloride."  The  formula  is  never 
correct  unless  the  sum  of  the  combining  numbers  on  one 
side  of  the  sign  of  equality  is  exactly  equal  to  the  sum 
on  the  other. 

HgCl2+  ZnI2   :  =  HgI2    +ZnCl2 

200  +  71        65+254      200+254       65  +  71 

271      +     319     =     454      +     136    =590 

Further,  if  we  have  given  the  left-hand  side  of  the 
equation,  and  one  product,  we  can  predict,  in  many 
cases,  what  the  other  product  will  be.  It  will  generally 
be  a  combination  of  the  elements  not  used  to  form  the 
product  given. 

In  this  book,  the  sign  -«-  placed  over  a  symbol,  indi- 
cates that  a  gas  is  evolved;  the  sign  v  placed  beneath, 
that  a  solid  is  formed  and  precipitates. 

Having  by  some  one  of  these  methods  obtained  a  new 
compound,  the  chemist  endeavors  to  confirm  the  conclu- 
sions he  has  reached  respecting  the  composition  of  the 
body,  by  again  separating  it  into  its  elements. 

IY.  —  ANALYSIS. 

18.  The  process  of  separating  a  compound  into  its 
constituents  is  called  analysis. 

Exp.  25.  —  Place  a  gramme  of  mercuric  oxide  in  a  tube  of  hard 
glass,  and  heat  strongly.  It  will  be  decomposed  into  mercury  and 
oxygen.  The  former  will  collect  in  metallic  globules  on  the  colder 
portions  of  the  tube,  and  the  latter  will  escape  as  a  gas.  The 
presence  of  oxygen  in  the  tube  may  be  tested  by  first  lighting  a 
splinter  of  pine,  then  blowing  it  out  so  as  to  leave  a  glowing  coal. 


24  CHEMISTRY. 

and  introducing  this  into  the  tube.  If  oxygen  is  present,  1;he  coal 
will  burst  into  a  flame.  The  oxygen  may  be  collected  by  previ- 
ously connecting  to  the  glass  tube,  by  means  of  a  perforated  cork, 
a  delivery  tube  which  dips  under  water  in  a  pneumatic  cistern, 
as  in  Fig.  6.  A  cylinder  filled  with  water  is  then  inverted  over 
the  mouth  of  the  delivery  tube.  As  fast  as  the  gas  is  evolved, 
it  rises  into  the  cylinder,  and  is  there  collected. 

Every  216  parts,  by  weight,  of  the   red   oxide   yields 
200  parts  of  mercury  and  16  of  oxygen,  also  by  weight. 


FIO.  6. 

Exp.  26. — Heat  iodic  anhydride  in  apparatus  similar  to  that 
shown  in  Fig.  6.  It  separates  into  oxygen  and  iodine.  The  iodine 
at  first  fills  the  tube  with  a  purple  vapor,  which  soon  condenses 
in  grayish-black  flakes.  The  oxygen  may  be  collected  and  exam- 
ined as  before. 

Every  334  parts,  by  weight,  of  iodic  acid  yields  254 
parts  of  iodine  and  80  of  oxygen. 

Exp.  27. — Heat  dry  mercuric  iodide  in  a  dry  test  tube.  It 
does  not  decompose, .  but  is  changed  to  vapor,  which  condenses  in 
yellow  crystals  near  the  top  of  the  tube.  This  is  called  sublimation. 
If  some  of  these  yellow  crystals  are  shaken  out  upon  paper  and 
rubbed  with  a  knife-blade,  they  become  red;  heated  again  upon  the 
paper,  they  become  yellow;  again  rubbed,  red;  and  so  on.  No 
chemical  change,  however,  has  taken  place. 

19.  Mere  change  of  temperature  will  not  suffice  for 
the  analysis  of  this  body.  We  may,  however,  determhie 
its  composition  indirectly.  Thus,  by  making  such  weigh- 
ings as  are  necessary,  we  may  ascertain,  in  Exp.  19, 


MATTER  INDESTRUCTIBLE.  25 

that  every  454  parts  of  mercuric  iodide  yields  254  parts 
of  iodine;  by  Exp.  21,  that  the  same  quantity  yields 
200  parts  of  mercury.  Also,  by  Exp.  22,  that  to  form 
454  parts  of  mercuric  iodide  requires  271  parts  of  mer- 
curic chloride  and  319  parts  of  zinc  iodide;  and,  by 
similar  experiments,  learn  that  271  parts  of  mercuric 
chloride  contain  exactly  200  parts  of  mercury,  and  that 
319  parts  of  zinc  iodide  contain  exactly  254  parts  of 
iodine.  Finally,  we  may  determine,  by  Exp.  11,  that 
the  exact  proportions  required  to  form  mercuric  iodide 
are  200  parts  of  mercury  and  254  parts  of  iodine. 
Since  all  these  agree,  we  are  certain  that  the  result  is 
correct. 

20.  When  reagents   are   employed   to   determine  what 
elements   are   present   in   a   body,  the  process   is   called 
qualitative   analysis.      When    reagents    are    employed    to 
determine  how  much  of  an  element  is  present  in  a  body, 
the  process  is  called  quantitative  analysis. 

21.  We  have   learned  by  these  experiments  that  dif- 
ferent substances  combine  with  different  degrees  of  energy. 
Phosphorus  and  iodine  unite  as  soon  as  they  are  brought 
in  contact.     Mercury  and  iodine  require  to  be  triturated, 
or  rubbed  together;    but,  once  united,  the  compound  is 
not  decomposed  by  heat.     On   the   other   hand,  the  red 
oxide  of  mercury  may  be  formed  by  prolonged  heating 
of  mercury  in  the  air,  at  a  temperature  of  about  315°  C., 
and   is   again  decomposed  into  its  constituents  at  a  dull 
red  heat. 

We  have  also  learned  that  the  same  matter  may  suc- 
cessively form  a  part  of  several  different  compounds. 
With  sufficient  care  in  experimenting,  we  can  follow  the 
same  matter  through  a  dozen  changes  without  losing  a 
particle.  No  matter  is  destroyed  by  chemical  changes, 
however  many  they  are,  or  however  violent  they  may 
appear. 


26  CHEMISTRY. 

Recapitulation. 

All  substances  are  either  simple  or  compound,  or  are  mixtures. 

(  electro-negative  I  non-metals,  13. 

Simple  substances  are     ...    J  (  semi-metals,  13. 

I  electro-positive  —  metals,  39. 
f  two  elements  —  binary. 
Comp/ound  substances  contain     <  three  elements  —  ternary. 

(^  four  elements — double  salts. 
In  binary  compounds  — 

The  negative  element  takes  the  termination  ide. 

It  may  take  the  prefix  mono,  di,  tri,  tetra,  or  penta. 

The  positive  element  may  take  the  termination  ous  or  ic. 

Chemical  changes  are  produced  — 

By  the  union  of  two  bodies Combination. 

By  displacing  one  element  by  another  ....  Substitution. 

By  an  interchange  of  elements Metathesis. 

By  the  decomposition  of  bodies Analysis. 

Analysis  is  either  Qualitative  or  Quantitative. 

The  laws  of  combination  are  — 

The  law  of  constant  proportions. 
The  law  of  multiple  proportions. 
The  law  of  combining  proportions. 


CHAPTEK   II. 

CHARACTERISTICS    OF    CHEMICAL    AFFINITY. 

22.  Few  of  the  elements  exist,  as  such,  free  in  nature. 
Gold,  platinum,  copper,  mercury,  silver,  sulphur,  and 
carbon  are  found  native,  but  most  of  the  others  have 
been  obtained  only  from  their  compounds.  The  un- 
stratified  portion  of  the  earth's  crust,  which  is  con- 
sidered to  be  the  source  from  which  the  other  rocks 
are  formed,  consists  mainly  of  the  compounds  of  eight 
elements,  although  it  contains  traces  of  many  others. 


COHESION.  2T 

The  principal  constituents  of  the  primary  rocks  are 
given  in  the  following  table,  together  with  the  weights 
of  each,  reckoned  on  a  scale  of  100  parts. 


Oxygen,  46.      Aluminium,  8. 
Silicon,    30.      Iron,  6. 


Calcium,  3.5.     Potassium,    2.4. 
Sodium,    2.5.     Magnesium,  1.4. 


We  find  in  the  stratified  rocks  minerals  containing 
comparatively  large  quantities  of  carbon,  sulphur,  arsenic, 
and  chlorine.  The  metals — copper,  lead,  zinc,  and  tin  — 
are  somewhat  abundant,  although  their  ores  are  sparsely 
distributed  in  mineral  veins. 

23,  The  waters  of  the  earth  are  composed  of  hydrogen 
and  oxygen,  but  contain    in    solution    notable   quantities 
of  sodium  chloride  and  other  salts. 

The  atmosphere  is  a  mixture  of  nitrogen,  oxygen,  and 
small  amounts  of  carbonic  anhydride  and  aqueous  vapor. 

Small  quantities  of  phosphorus  are  found  in  plants 
and  animals. 

The  nineteen  elements  named  are  the  only  ones  which 
are  found  in  great  abundance.  The  greater  portion  of 
the  remaining  elements  are  seldom  met  with,  and  some 
of  these  are  so  rare  that  they  have  been  handled  by 
but  few  chemists. 

24.  The  force  which  holds  like  particles  of  matter  to- 
gether is  called  cohesion.     It  is  strongly  exerted  in  solids, 
feebly  in  liquids,  and  appears   to   be   entirely  absent  in 
gases.     The  energy  of  cohesion  is  dependent :  (1)  on  the 
kind  of  matter ;  thus,  it  is  evident  that  the  particles  of 
iron  cohere  with  greater  energy  than  those  of  lead,  be- 
cause  it   requires   a   greater   force   to   pull  them  apart: 
(2)    on   the    temperature;    water,    a   liquid    at   ordinary 
temperatures,  changes  in  the  cold  of  winter  to  solid  ice, 
and,  on  boiling,  passes  away  in  aeriform  steam :  (3)  fluids 
are  greatly  influenced  by  pressure ;  thus,  if  ether,  a  liquid, 
under  the  pressure  of  one  atmosphere,  be  introduced  into 


28  CHEMISTRY. 

the  vacuum  at  the  top  of  a  barometer  tube,  it  instantly 
changes  to  vapor.  (See  Norton's  Nat.  Philos.,  Art.  569). 
The  cohesion  of  any  substance  is,  therefore,  only  relative. 

25.  Fifty-eight  elements  are,  at  ordinary  temperatures, 
solids ;  but  even  refractory  solids,  like  copper,  silver, 
and  gold,  have  been  melted  and  volatilized.  Mercury 
and  bromine,  the  only  elements  which  are  ordinarily 
liquid,  easily  vaporize  and  are  as  easily  solidified  by 
comparatively  slight  changes  in  temperature.  Under 
the  joint  influence  of  cold  and  pressure,  chlorine,  a 
gaseous  element,  becomes  liquid ;  and  some  compound 
gases,  like  ammonia  and  carbonic  anhydride,  become 
not  only  liquid,  but  solid. 

Gases  like  these  are  called  coercible  gases.*  The  re- 
sources of  experiment  have  lately  availed  to  condense 
oxygen,  nitrogen,  and  hydrogen.  These  elements,  how- 
ever, from  the  difficulty  experienced  in  condensing  them, 
are  frequently  spoken  of  as  the  permanent  gases.  It  is 
probable  that  any  one  of  the  elements  may  be  obtained 
in  either  the  solid,  liquid,  or  aeriform  condition.  This 
statement  is  also  true  of  many  compounds ;  but  a  large 

*  The  following  gases  are  condensed  to  liquids  at  a  temperature  of  0°  C.,  under 
the  atmospheric  pressures  named  below : 


PRESSURE 

IN  ATMOS- 
PHERES. 

Sulphurous  anhydride,  SO2  1.53 

Cyanogen,  CN  2.37 

Ammonia,  NH3  4.40 

Chlorine,  Cl  6. 


PRESSURE 

IN  ATMOS- 
PHERES. 

Sulphuretted  hydrogen,  H2S  10. 

Hydrochloric  acid  gas,  HC1  20.20 

Nitrous  oxide,  N2O  32.20 

Carbonic  anhydride,  CO2  38.50 


The  following  bodies  have  been  condensed  to  liquids  under  a  pressure  of 
one  atmosphere,  at  the  temperatures  given  below : 


Carbonic  anhydride,  — 78°  C. 

Chlorine,  —  35° 

Cyanogen,  —  21° 

Sulphurous  anhydride,  — 10° 


Bromine,  +    63°  C. 

Water,  +  100° 

Iodine,  +  200° 

Mercury,  -f  350° 


In  condensing  gases  it  is  usual  to  employ  conjointly,  when  possible,  the  effect 
of  cold  and  of  pressure.  O  is  condensed  at  — 140°  under  a  pressure  of  320  atmos- 
pheres ;  N,  at  +  13°,  and  under  200  atmospheres.  When  H  was  allowed  to  ex- 
pand suddenly  from  a  pressure  of  280  atmospheres,  it  apparently  formed  solid 
.particles  described  as  "hail."  The  cold  produced  by  the  sudden  expansion 
must  have  been  very  great. 


AFFINITY.  29 

number  of  these  bodies,  of  which  marble  and  wood  are 
examples,  are  so  readily  decomposed  by  heat,  that  we 
can  not  hope  to  volatilize  them. 

It  is  well  to  remark  that  in  chemistry  no  distinction 
is  drawn  between  gases  and  vapors. 

26.  The  force  which  unites  unlike  particles  of  matter, 
and   keeps   them   in   combination,   is   called   affinity.     It 
acts  between  different  substances  with  a  different  amount 
of  energy,  and  is  modified  by  the  other  molecular  forces. 
Although  most  of  the  experiments  in  this  book  illustrate 
the  characteristics  of  chemical  affinity,  the  following  ex- 
amples are   given   to   familiarize  the  student  with  some 
of  the  most  important. 

27.  Affinity  varies   with  the  kind   of  matter.     Iodine 
readily  unites  with  the  metals,  but   all   metallic  iodides 
are    decomposed    by    free    chlorine,    showing    that    the 
affinity  of  chlorine   for   metals  is  stronger  than  that  of 
iodine.     Nevertheless,  iodine  has  a  stronger  affinity  for 
oxygen  than  chorine  has. 

Exp  28. — Add  weak  chlorine  water  to  a  solution  of  potassium 
iodide,  to  which  some  boiled  starch  has  been  added.  The  blue  color 
which  is  produced  shows  the  presence  of  free  iodine.* 

28.  It  is  influenced  by  the  mass  or  the  excess  of  one 
substance.      Sulphuric    acid    has    generally    a    stronger 
affinity  for  metallic  oxides  than  hydrochloric  acid;    but 
if  to    a    solution    of  blue    sulphate    of  copper    a    large 
amount  of  hydrochloric  acid  be  added,  the  solution  will 
change  to  a  green  color.     This   shows  that  cupric  chlo- 
ride has  been  formed,  although,  at   the   same  time,  sul- 
phuric acid  must  have  been  set  free.     The   result   must 
be  attributed   to  the  excess  in   quantity  of  the  hydro- 
chloric acid. 

*  KI  +  ci  =  KCI  +  i. 


30 


CHEMISTRY. 


Exp.  29. Fill  a  hard  glass  tube  with  iron  turnings;  place  this 

in  a  furnace  and  heat  to  redness.  (Fig.  7).  Now  pass  through 
the  tube  a  current  of  steam.  The  water  will  be  decomposed;  its 
oxygen  unites  with  the  iron  to  form  an  oxide  of  iron;  hydrogen  is 
liberated,  and  may  be  collected  at  the  other  end  of  the  tube.  * 


FIG.  7. 

Exp.  30. — When  the  iron  is  well  oxidized,  replace  the  steam 
by  a  current  of  dry  hydrogen:  the  operation  is  reversed.  The 
oxide  of  iron  is  reduced  to  metallic  iron,  and  steam  passes  out  of 
the  other  end  of  the  tube,  or  collects  as  drops  of  water  in  the 
colder  portions.! 

In  the  first  instance,  the  iron  is  enveloped  by  steam, 
and  the  hydrogen  is  at  once  removed  from  the  sphere 
of  action.  In  the  second  instance,  the  hydrogen  is  in 
greater  quantity,  and  the  steam  formed  is  prevented  from 
acting  upon  the  iron. 

29.  The  same  element  does  not  exhibit  the  same  energy 
under  all  circumstances.  Thus,  if  hydrogen  be  passed 
into  water  which  contains  iodine  in  suspension,  no  action 
will  take  place.  Neither  does  iodine  decompose  water 
to  unite  with  its  hydrogen.  If,  however,  iodine  is  placed 
in  water,  together  with  some  other  substance  that  is  ca- 


*4  HgO  +  3  Fe  =  Fe3O4  +  4  H2. 


t4  H2  +  Fe3O4  =  4  H2O  +  3  Fe. 


AFFINITY.  31 

pable  of  uniting  with  the  oxygen  of  the  water,  it  readily 
unites  with  the  hydrogen  that  is  liberated. 

Exp.  31. — Add  a  few  flakes  of  iodine  to  a  solution  of  potassium 
iodide.  They  will  dissolve,  on  stirring,  to  form  a  blood-red  liquid. 
Now  add  this,  drop  by  drop,  to  a  very  dilute  solution  of  sulphurous 
acid  or  of  sodium  hyposulphite,  previously  mixed  with  a  very  little 
boiled  starch.  The  sulphurous  acid  changes  to  sulphuric  acid  by 
uniting  with  the  oxygen  of  the  water.*  Hydrogen  is  liberated,  and, 
at  the  same  instant,  unites  with  the  iodine  to  form  hydriodic  acid.f 
So  long  as  this  reaction  continues,  the  liquid  remains  colorless;  but 
as  soon  as  all  the  sulphurous  acid  is  consumed,  the  starch  will  form 
a  blue  color  with  the  free  iodine. 

In  this  experiment  the  hydrogen  is  said  to  be  in  the 
nascent  state;  that  is,  in  the  state  of  being  liberated. 
All  bodies  in  this  state  have  much  stronger  affinities 
than  when  they  are  used  in  an  isolated  form. 

Affinity  is  also  influenced  by  the  state  of  division 
of  matter. 

Exp.  32. — Dissolve  a  few  small  pieces  of  phosphorus  in  car- 
bonic disulphide.  Dip  a  feather  into  this  solution  and  then  draw  it 
quickly  over  dry  paper.  The  carbonic  disulphide  soon  evaporates 
and  leaves  the  phosphorus  in  a  finely  divided  state  on  the  paper. 
This  exposes  so  much  surface  to  the  action  of  the  air,  that  the 
phosphorus  and  oxygen  combine  rapidly  and  burst  into  a  flame. 

Exp.  33. — Put  some  alcohol  in  a  saucer  and  set  it  on  fire. 
Gunpowder  may  be  dropped  through  the  flame  without  igniting. 
If,  however,  fine  iron  filings  be  dropped  into  the  flame,  they  will 
burn  with  bright  scintillations.  (See  Exp.  194). 

30,  Affinity,  like  cohesion  and  adhesion,  increases  with 
the  extent  of  surface  exposed  to  its  action,  and  is,  there- 
fore, generally  the  more  energetic  the  more  finely  pul- 
verized the  bodies  are  which  are  acted  upon.  An  ap- 
parent exception  to  this  is  found  in  the  fact  that  a  heap 

*  H2O  +  H2SO3  =  H2SO4  +  H2. 

f  H2  +  I2  =  2HI ;  or  together,  H2O  +  H?SO3  +  I?  =  H2SO4  +  2HI. 


32  CHEMISTRY. 

of  charcoal  dust  will  burn  less  readily  than  one  of  lump 
charcoal.  This  is  easily  explained ;  for  the  lump  char- 
coal permits  the  air  to  circulate  freely  between  its  in- 
terstices, and  thereby  exposes  a  larger  surface  than  the 
charcoal  dust,  which  can  be  enkindled  only  on  the  out- 
side of  the  heap. 

31.  Affinity  varies  with  the  state  of  cohesion.     Chem- 
ical affinity  acts  only  at  insensible  distances.     The  more 
points   of  contact,  the   more  readily  will   bodies  unite. 
Any  thing  that  tends   to   overcome   the   cohesion   of  a 
body  tends  also  to  augment  its  affinity  for  other  bodies. 
Generally  speaking,  two  solids  can  not  be  made  to  unite 
by  pulverizing  them  together;   the  principal  exceptions 
being  those   cases   in  which  a  liquid  is  set  free  by  the 
reaction. 

Exp.  34. — Rub  together  in  a  mortar  crystals  of  oxalic  acid 
and  caustic  lime.  The  two  may  be  made  to  unite,  because,  at  the  be- 
ginning of  the  action,  a  little  of  the  water  of  crystallization  of  the 
acid  is  set  free,  and  acts  as  a  solvent. 

Exp.  34.  (a)— Rub  together  5  parts  of  KI  and  4  parts  of  HgCl2. 
They  will  combine  to  form  red  HgI2  and  KC1.  This  is  a  marked 
exception. 

Exp.  35. — Rub  together  oxalic  acid  and  sodium  carbonate.  No 
apparent  action  takes  place ;  but,  if  a  little  water  be  added,  the  two 
unite  with  a  rapid  evolution  of  carbonic  anhydride. 

32,  It  is  a  general  principle  that  to  produce  combina- 
tion, at  least  one  of  the  bodies  must  be  in  the  fluid  state. 
We  have  seen  that  the  cohesion  of  solids  is  overcome  by 
heat  liquefying    or   vaporizing   them.     It   may   also   be 
overcome  by  the  adhesion  of  liquid  particles,  producing 
Vvhat  is  termed  a  solution. 

Exp.  36. — Pulverize  20  grammes  of  common  alum;  place  it  in 
a  flask,  and  pour  over  this  50  grammes  of  cold  water.  The  whole 
of  the  alum  will  not  dissolve,  even  after  repeated  stirring.  Now 
heat  the  flask,  and  all  will  dissolve.  The  solution  has  a  sweet 
and  astringent  taste. 


SOLUTIONS.  33 

Exp.    37. — Set   the   solution    away   to   cool:    small,   octahedral 
crystals  are  speedily  formed  (see  Fig.  8);    and,  if  the 
liquid  is   cooled  to  the   freezing  point,  nearly  all  the 
alum  will  crystallize  out. 


Such  simple  solutions  can  not  be  regarded 
as  due  to  chemical  reactions ;    for,  excepting 
the  mere  liquefying  of  the   solid,  no  change        FIG.  8. 
has  been  produced  in  its  properties. 

When  a  solution  contains  as  much  solid  matter  as  it 
is  capable  of  dissolving  at  any  given  temperature,  it  is 
said  to  be  saturated.  Common  salt  is  about  equally 
soluble  at  all  temperatures.  Some  bodies  are  more  solu- 
ble at  a  particular  temperature  than  either  above  or 
below  it.  Thus,  the  solubility  of  sodium  sulphate  in- 
creases from  0°  C.  to  33°  C.,  and  then  diminishes;  but 
the  solubility  of  most  bodies  is  increased  by  an  eleva- 
tion of  temperature.  Marked  exceptions  are  found  in 
some  lime  compounds. 

Exp.  38. — Put  a  tablespoonful  of  slaked  lime  into  a  pint  flask; 
fill  with  water,  and  shake  the  flask  for  some  time  vigorously.  Now 
let  it  stand  undisturbed  until  the  excess  of  lime  has  entirely  settled 
to  the  bottom.  Then  pour  a  little  of  the  supernatant  fluid  into  a 
test  tube  and  heat.  It  will  soon  become  cloudy,  showing  that  hot 
water  is  not  as  good  a  solvent  for  caustic  lime  as  cold  water. 

33.  Simple   solutions   are   generally   attended   by   the 
absorption   of  heat,  due  to  the   passage   of  the  solid  to 
the  liquid  condition. 

Exp.  39. — Mix  two  pounds  of  snow  with  one  pound  of  common 
salt.  Both  will  partially  dissolve,  and  a  "freezing  mixture"  will 
be  produced  capable  of  congealing  water.  A  pleasing  way  of  show- 
ing this  is  to  select  two  test  tubes  of  not  quite  the  same  size,  and, 
having  put  a  little  water  in  the  larger,  place  the  smaller  within 
it.  By  stirring  the  mixture  with  this  apparatus,  a  little  cup  of  ice 
will  be  formed  between  the  tubes. 

34.  There  are  two  kinds   of  solutions :    (1)  the  simple 
solutions,  which   have    already  been   described,   and    (2) 

Chcm.— 3. 


34 


CHEMISTRY. 


FIG.  9. 


chemical  solutions,  in  which  the  body  first  enters  into  a 
new  chemical  compound,  which  is  then 
dissolved.  In  chemical  solutions,  al- 
though heat  facilitates  the  formation 
of  the  solution,  the  quantity  of  the  body 
dissolved  is  always  dependent  on  the 
quantity  of  the  solvent  present;  be- 
cause the  proportions  in  which  bodies 
combine  are  invariable,  and  are  not 
affected  by  differences  in  tempera- 
ture. So,  also,  a  chemical  solution 
generally  liberates  heat. 

Exp.  40. — Place  a  teaspoonful  of  copper 
filings  in  a  test  tube,  and  cover  them  with 
strong  nitric  acid  (Fig.  0).  Copious  red  fumes 
will  be  given  oft*  the  tube  will  become  warm, 
and,  if  enough  acid  be  added,  all  the  copper  will  disappear  in  the 
liquid.  If  this  be  evaporated,  crystals  of  cupric  nitrate  may  be 
obtained.* 

The  liquids  used  to  produce  chemical  solutions  are 
generally  acids.  In  some  cases,  aqueous  solutions  of  the 
alkalies,  or  of  the  alkaline  sulphides,  are  employed. 

35.  The  solvents  suitable  in  any  given  case,  either 
for  simple  or  chemical  solutions,  are  to  be  learned  only 
in  detail.  Water  is  the  best  solvent  for  compounds  of 
the  metals;  alcohol  and  ether  are  good  solvents  for 
most  organic  compounds;  chloroform  and  carbonic  di- 
sulphide  dissolve  iodine  and  phosphorus. 

The  solvent  powers  of  liquids  have  a  wide  range. 
Water  dissolves  all  normal  nitrates  and  chlorates;  all 
chlorides  except  those  of  silver,  lead,  thallium,  and  the 
cuprous  and  mercurous  chlorides;  and  most  sulphates  — 
those  of  barium,  strontium,  lime,  and  lead  being  promi- 
nent exceptions.  Some  bodies,  like  calcium  chloride  and 


:3Cu.  f  4(H2O,  N2O5)  +  air  =  3(CuO,  N,,O5)  +  4II2O 


SOLUTIONS. 


35 


zinc  chloride,  are  so  soluble  that,  if  placed  in  an  open 
vessel,  they  attract  enough  water  from  the  air  to  form 
a  solution.  Such  bodies  arc  called  deliquescent. 

36.  Liquids  also  dissolve  one  another:  alcohol  and 
water,  in  all  proportions;  ether  and  water,  in  propor- 
tions of  about  one-tenth  of  each.  Benzene  dissolves 
many  oils,  and  very  many  of  the  oils  are  good  solvents 
for  each  other. 

Solutions  of  gases  are  made  by  passing  the  gas  into 
cold  water  or  other  liquids.*  Gases  are  generally  ab- 
sorbed more  abundantly  by  cold  water  than  by  warm 
wrater.  If  a  solution  of  gases  be  warmed,  some  of  the 
gas  is  driven  off,  and  at  the  boiling  temperature,  all  of 
the  gas  is  expelled.  Boiled  or  distilled  water  tastes 
"  flat,"  because  of  the  absence  of  the  gases  usually  found 
in  well  water.  The  gases  also  escape  when  the  solu- 
tions which  contain  them  are  frozen ;  that  is,  when  the 
water  becomes  solid. 

If  the  temperature  remains  unchanged,  it  is  also  true, 
within  certain  limits,  that  the  weight  of  a  gas  absorbed 
by  water  increases  with  the  pressure.  The  volume  of 
the  gas  absorbed  remains  the  same,  because  the  pressure 
to  which  it  is  subjected  condenses  it. 

*  The  following  table  shows  how  many  volumes  of  the  gases  named  are  ab- 
sorbed by  one  volume  of  water  and  of  alcohol,  \mder  the  pressure  of  one  atmos- 
phere, or  at  760  mm.  Barometer. 

COEFFICIENT   OF   ABSORPTION. 


WATER. 

ALCOHOL. 

At  0°  C. 

At  10°  C. 

At  0°  C. 

At  10°  C. 

Hydrogen, 

H 

0.0193 

0.0193 

0.02569 

0.06786 

Nitrogen, 

N 

0.02035 

0.01607 

0.12634 

0.12276 

Oxygen, 

0 

0.04114 

0.03250 

0.28397 

0.28397 

Atmospheric  air, 

0.0247 

0.01953 

Carbonic  anhydride, 

CO2 

1.7967 

1.1847 

4.3295 

3.5140 

Hydrogen  sulphide, 

H2S 

4.3706 

3.5838, 

17.891 

11.9922 

Sulphurous  anhydride, 

S02 

78.789 

56.647 

328.62 

190.21 

Hydrochloric  acid, 

HC1 

500. 

418. 

Ammonia, 

NH3 

1050. 

813. 

36  CHEMISTRY. 

Thus,  water  at  15°  C.  takes  up  its  own  bulk  of  carbonic  anhy- 
dride, or  about  -^^  part  of  its  weight.  Under  pressure  of  two  at- 
mospheres, it  absorbs  -%^-Q  of  its  weight;  of  four  atmospheres,  TJ- 
of  its  weight,  etc.  The  "  soda  water  "  of  the  confectioner  is  water 
charged  with  carbonic  anhydride  under  pressure.  When  the  pressure 
is  removed,  the  greater  part  of  the  gas  escapes  with  effervescence, 
because  the  gas  resumes  its  former  volume. 

37.  When  two  bodies  have  a  tendency  to  react  upon 
each  other,  the  affinity  between  them  is  greatly  modified 
by  the  natural  cohesion  of  the  product. 

Berthollet's  first  law :  Solutions  of  two  compounds  can 
not  be  mixed  together  without  a  double  decomposition  taking 
place,  if  any  two  of  the  constituents  can  form  an  insoluble 
compound. 

We  have  already  had  an  example  that  corroborates 
this,  in  Exp.  22.  Mercuric  chloride  is  soluble,  and  mer- 
curic iodide  is  insoluble,  in  water;  hence,  if  mercuric 
chloride  is  mixed  with  any  solution  containing  a  soluble 
iodide,  mercuric  iodide  will  be  formed,  although  we 
know,  by  Exp.  19,  that  the  affinity  of  mercury  for  free 
chlorine  is  stronger  than  for  free  iodine. 

Exp.  41. — Mix  a  solution  of  mercuric  chloride  with  a  solution 
of  potassium  iodide.  Mercuric  iodide  will  be  separated.  The  ex- 
periment may  be  repeated  with  sodium  iodide  or  zinc  iodide. 

38.  The  formation   of  a   solid  insoluble  in  the  liquids 
mixed  together  is  called  precipitation.     The  solid  which 
separates  is  called  a  precipitate. 

Exp.  42. — Make  an  alcoholic  solution  of  potassium  acetate,  and 
pass  into  this  a  stream  of  carbonic  anhydride:  potassium  carbonate 
will  precipitate,  because  it  is  insoluble  in  alcohol,  and  acetic  acid 
will  be  set  free. 

Exp.  43. — Add  acetic  acid  to  an  aqueous  solution  of  potassium 
carbonate.  The  reaction  will  be  reversed:  viz.,  potassium  acetate 
will  be  formed,  and  carbonic  anhydride  will  be  set  free  as  a  gas. 


BERTHOLLETS  LAWS.  37 

We  may  explain  the  last  reaction  thus:  (1)  the  acetic  acid  has 
a  stronger  affinity  for  potassium  than  carbonic  anhydride;  or  (2) 
carbonic  anhydride  is  but  slightly  soluble  in  water,  and  is,  besides, 
naturally  an  aeriform  body. 

39.  The  volatility  of  the   product  certainly  influences 
affinity.     Thus,   limestone   or   calcium    carbonate,    when 
strongly  heated,   breaks  up  into  calcium  oxide  and  car- 
bonic anhydride. 

Berthollet's  second  law:  If  any  two  bodies  whose  con- 
stituents are  capable  of  interchanging  and  forming  a  volatile 
product  are  heated  together,  these  constituents  will  unite  and 
volatilize. 

Exp.  44. — Add  to  a  solution  of  calcium  chloride  a  solution  of 
ammonium  carbonate.  Calcium  carbonate  will  precipitate,  and 
ammonium  chloride  remain  dissolved  in  the  liquid.* 

Exp.  45. — Heat  together  an  intimate  mixture  of  powdered  cal- 
cium carbonate  and  ammonium  chloride.  At  a  temperature  a  little 
above  100°  C.,  calcium  chloride  and  ammonium  carbonate  will  be 
formed:  the  latter  is  volatile  and  escapes.f 

The  reaction  in  Exp.  42  is  explained  by  the  first  law — an  in- 
soluble precipitate  is  formed:  the  reaction  in  Exp.  43,  by  the  second 
law — a  volatile  product  is  formed. 

40.  Affinity  is  in  some  cases  influenced  by  adhesion. 

Exp.  46. — Platinum  sponge  affords  such  an  extent  of  surface 
to  the  air,  that  a  small  piece  contains  a  large  quantity  of  absorbed 
oxygen.  If  the  dried  sponge  be  brought  near  a  current  of  dry 
hydrogen,  the  two  gases  are  brought  so  close  together  that  they 
unite,  and  the  hydrogen  is  enkindled. 

Instances  are  known  of  greasy  rags,  heaped  together, 
taking  fire  spontaneously  within  twenty-four  hours.  The 
spontaneous  combustion  of  porous  bodies  like  cotton  or 
sawdust  saturated  with  oil  is  not  infrequent,  and  is  due 

*CaCl2  +  (NH4)2CO3  =  2NH4C1  +  CaTO3. 
t  CaCO3  +  2NH4C1  =  CaCl2  +  (N 


38  CHEMISTRY. 

to  a  similar  cause.  These  bodies  condense  the  air 
within  their  pores ;  oxidation  commences  and  liberates 
a  small  quantity  of  heat ;  this  accelerates  the  oxidation, 
and  thus  the  process  goes  on  with  increasing  rapidity 
until  the  mass  bursts  into  a  flame. 

41.  Affinity  is  influenced  by  heat  This  influence  may 
be  indirect,  as  when,  in  liquefying  bodies,  the  heat  is 
applied  to  overcome  cohesion ;  but  there  are  many  cases 
in  which  it  acts  directly. 

Exp.  47.— Endeavor  to  light  the  gas  from  an  ordinary  burner 
by  a  hot  iron  rod.  The  gas  will  not  ignite  until  the  iron  is  at  a 
bright  red  heat. 

The  temperature  at  which  bodies  enter  into  combina- 
tion with  the  oxygen  of  the  air,  so  as  to  produce  igni- 
tion, varies  greatly.  No  heat  is  sufficient  to  ignite 
iodine,  chlorine,  or  bromine  in  the  air  or  in  oxygen 
gas.  Most  of  the  elements  require  to  be  heated  before 
they  take  fire.  Sulphur  ignites  at  about  285°  C. ;  car- 
bonic disulphide  vapor  is  ignited  by  a  warm  glass  rod, 
heated  to  149°  C. ;  phosphorous  is  ignited  at  about  60°  C. 
A  match  tipped  with  phosphorous  is  sufficiently  heated 
by  gentle  friction  to  ignite. 

Exp.  48. — Place  a  slip  of  dried  phosphorus  on  a  chip  of  wood. 
.  Fill  a  test  tube  with  boiling  water.  Touch  the  phosphorus  with 
the  end  of  the  tube  and  it  will  ignite. 

A  certain  temperature  is  therefore  sometimes  necessary 
to  induce  combination.  When  the  chemical  action  is 
once  well  begun,  the  heat  developed  by  the  union  of 
the  bodies  is  usually  sufficient  to  continue  it ;  but,  if 
this  is  not  the  case,  or  if  the  heat  evolved  be  too  rap- 
idly conducted  away,  the  action  ceases. 

Exp.  49. — Conduct  a  stream  of  dry  ammonia  gas  *  into  the  jet 

*This  may  be  obtained  by  heating  ordinary  ammonium  hydrate  in  a  small 
flask,  and  conducting  the  vapor  through  a  tube  filled  with  small  lumps  of 
quicklime  to  dry  it. 


TEMPERATURE  OF  IGNITION. 


39 


of  a  Bunsen's  burner;  it  will  burn  with  a  pale  flame,  which  is  ex- 
tinguished as  soon  as  the  burner  is  taken  away. 

If  the  ammonia  is  heated  by  passing  it  through  a  hot  tube,  the 
flame  will  be  continuous. 


FIG.  10. 

Exp.  50. — Bring  a  cold  white  plate  over  an  ignited  gas  jet. 
Soot  will  be  deposited,  because  the  plate  reduces  the  temperature 
below  that  required  for  the  ignition  of  the  carbon  present  in  the 
flame. 

Exp.  51. — Bring  a  sheet  of  fine  wire 
gauze  over  an  ignited  jet  of  coal  gas. 
The  flame  is  arrested  at  the  under  sur- 
face of  the  gauze,  because  the  metal 
conducts  away  so  much  of  the  heat  that 
the  temperature  of  the  gas  which  passes 
through  the  gauze  is  lower  than  that 
necessary  to  effect  combination  between  the  gas  and  the  oxygen 
of  the  air.  Unignited  gas  passes  through,  as  may  be  shown  by 
igniting  it  above  the  gauze. 

Exp.  52. — The  gas  may  be  ignited 
above  the  gauze  without  igniting  the  jet 
below,  as  shown  in  Fig.  12. 


FIG.  11. 


42.  Heat  also  effects  decomposi- 
tion, We  have  already  seen,  by 
Exp.  25,  that  a  mercuric  oxide  is 
decomposed  by  heat,  although  a 
less  heat  is  sufficient  to  produce 
combination  of  the  same  elements.  So,  also,  limestone, 


40  CHEMISTRY. 

or  calcium  carbonate,  is  decomposed  by  strong  heat  into 
quicklime  and  carbonic  anhydride,  although  the  affinity 
between  the  two  is  at  ordinary  temperatures  so  great 
that  quicklime  exposed  to  the  air  absorbs  the  carbonic 
anhydride  contained  in  it,  and  again  forms  calcium 
carbonate. 

Exp.  53. — If  a  stream  of  carbonic  anhydride  is  passed  over 
sodium  gently  heated,  it  is  decomposed  with  the  formation  of 
sodium  oxide  and  carbon  (Exp.  172);  and  a  mixture  of  carbon  and 
sodium  oxide,  strongly  heated,  yields  again  sodium  and  an  oxide  of 
carbon  (§353).  At  ordinary  temperatures  the  affinities  of  carbon  are 
feeble,  but  at  white  heat  they  are  among  the  strongest  known. 

43.  Chemical  combination  is  usually  attended  by  the 
evolution  of  heat,  and  sometimes  also  of  light.  When 
a  substance  combines  with  the  oxygen  of  the  air  so 
rapidly  as  to  evolve  light,  we  call  the  process  com- 
bustion, and  say  that  the  substance  burns.  Thus,  we 
say  a  piece  of  ignited  sulphur  burns;  but  when  a 
metal  combines  slowly  with  the  oxygen  and  no  light 
is  evolved,  we  say  the  metal  corrodes,  or  rusts.  Thus, 
a  piece  of  iron  rusts  in  moist  air.  In  chemical  lan- 
guage, both  of  these  processes  are  examples  of  com- 
bustion ;  and  so,  also,  true  com- 
bustion can  take  place  when  no 
oxygen  is  present. 


.  54. — Strongly  heat  in  a  wide- 
mouthed  flask  a  little  sulphur,  until  the 
flask  is  filled  with  sulphur  vapor.  Also 
heat  a  strip  of  thin  copper  foil  and 
plurtge  it  quickly  into  the  sulphur  vapor. 
The  two  elements  combine  and.  evolve 
heat  and  light. 

It  was  formerly  the   custom   to 

classify  bodies  as  combustible  bodies 
FIG.  13. 

and   supporters  of  combustion;   but 

these  terms  are  manifestly  inappropriate ;  because,  when 


HEAT  OF   COMBINATION. 


41' 


sulphur  burns  in  air,  we  should  have  to  call  sulphur  the 
combustible  body,  and,  when  copper  burns  in  sulphur, 
the  sulphur  is  the  supporter  of  combustion.  Combustion 
is,  in  fact,  due  to  chemical  combination  in  which  both 
bodies  play  an  equal  or  reciprocal  part. 

Ordinarily,  coal  gas  may  be  said  to  burn  in  air,  but 
air  will  also  burn  in  an  atmosphere  of  coal  gas. 

Exp.  55, — Fit  a  perforated 
cork  to  an  ordinary  lamp  chim- 
ney, and  attach  this  to  a  gas 
burner,  as  shown  in  Fig.  14. 
Fill  a  gas  bag  or  a  large  blad- 
der with  air,  and  attach  to  its 
mouth  a  tube  drawn  out  so  as 
to  yield  a  very  small  jet.  Turn 
on  the  gas,  and  after  it  has  es- 
caped for  some  time,  ignite  it. 
Now  bring  the  jet  of  the  bag 
to  the  top  of  the  chimney  and 
force  out  the  air.  It  will  ignite, 
and  may  then  be  depressed  in 
the  chimney.  The  air  will  con- 
tinue to  burn  at  the  jet. 

In  this  case,  as  well  as  in  the 

ordinary  process,  the  combustion  takes  place  where  the  two  gases 
meet  and  enter  into  combination. 

44.  The  heat  of  combination  varies  with  the  bodies 
that  are  brought  in  combination  and  the  product 
formed ;  *  but  it  is  important  to  observe  that  the  same 
amount  of  heat  will  ultimately  be  evolved,  whether  the 
union  takes  place  rapidly  or  slowly;  only,  in  the  latter 
case,  it  may  not  be  possible  to  measure  the  heat. 

The  heat  of  combination  may  be  measured  in  thermal 
units.  A  thermal  unit  is  the  heat  required  to  raise  one 
pound  (or  one  gramme)  of  water  from  0°  C.  to  1°  C. 

*  It  is  probable  that  the  relation  between  heat  and  chemical  action  will 
soon  become  an  important  factor  in  theoretical  chemistry;  but,  as  yet,  the 
results  reached  are  of  interest  mainly  to  advanced  students. 


FIG.  14. 


42 


CHEMISTRY. 


The  following  table  gives  some  of  the  results  obtained 
by  burning  the  substances  named  in  oxygen,  chlorine, 
and  iodine  vapor. 

HEAT  DEVELOPED  BY  COMBINATION 
I.   WITH  OXYGEN. 

ONE  POUND          COMPOL'Xn  THERMAL       ONK   1'OUXD         COMPOVND  THERMAL. 

OF  FOKMKD.  1'NITS.  OF  iORMF.l).  UNITS. 


Hydrogen 

Carbon 

Phosphorus 


H20 
CO, 


34462 
8080 
5747 


Sulphur 

Zinc 

Iron 


Hydrogen         HC1 
Phosphorus      P2C15? 


Zinc 


Znl. 


II.   WITH  CHLORINE. 

23783    I    Zinc 
3422?  I    Iron 

III.   WITH  IODINE. 

819    I    Iron 


S02 
ZnO 
Fe304 


ZnCla 
FeuCl6 


Fe2I6 


2220 
1330 
1582 


1529 
1745 


4G3 


The  ordinary  combust4on  of  wood,  coals,  and  oils  are 
familiar  examples  of  combustion.  These  bodies  are  gen- 
erally compounds  of  carbon  and  hydrogen.  In  burning, 
they  are  first  decomposed,  and  then  unite  with  the  oxy- 
gen of  the  air  to  form  water  and  carbonic  anhydride. 

We  may  also  remark  that  heat  is  frequently  evolved 
in  the  processes  of  substitution  and  double  decomposi- 
tion ;  and  sometimes  also  by  direct  decomposition,  as 
when  gun  cotton  explodes.* 

*  In  considering  these  relations  of  heat,  we  may  have  regard  to  three  points: 
(1)  The  temperature  of  ignition;  (2)  The  heat  of  combination,  or  the  calorific 
value  of  a  substance;  and  (3)  The  temperature  attained.  This  last  may  be 
found  theoretically,  by  dividing  its  available  calorific  value  by  the  product 
found  by  multiplying  together  the  weight  of  the  compound  formed  and  its 
specific  heat.  Thus,  one  pound  of  hydrogen  burning  in  oxygen  evolves  34462 
thermal  units.  The  9  pounds  of  steam  which  are  formed  render  latent  537  X  9 
=  4833  thermal  units.  The  calorific  value  of  the  hydrogen  remaining  will  be 
34462  —  4833  =  29629  thermal  units,  which  are  available  for  raising  the  tem- 
perature of  9  pounds  of  steam.  Now,  as  the  specific  heat  of  steam  is  048,  it 
will  require  0.48  X  9  =  4.32  thermal  units  to  raise  the  9  pounds  1°  C.  Finally, 
dividing  the  available  calorific  value  29629  by  4.32,  we  obtain  6930°  C.,  as  the 
temperature  to  be  attained  by  hydrogen  burning  in  oxygen.  It  is  needless 


INFLUENCE  OF  LIGHT. 


43 


45.  Affinity  is  sometimes  influenced  by  light.  Light 
plays  an  important  part  in  the  chemical  processes  of 
nature,  being  necessary  to  the  vigorous  growth  of  plants, 
and  contributing  riot  a  little  to  the  health  of  animals. 
It  is  not  without  influence  in  the  operations  of  a  chem- 
ical laboratory. 

Exp.  56. — Fill  a  clear  glass  bottle 
with  a  mixture  of  equal  parts  of  chlorine 
and  hydrogen,  in  a  darkened  room,  and 
cork  the  bottle  tightly.  Wrap  it  in  thick 
folds  of  cloth,  and,  having  brought  it  out 
into  bright  sunlight,  stand  at  a  distance 
and  pull  off  the  cloth  by  means  of  a  string 
previously  attached  to  it.  The  gases  will 
instantly  combine  with  explosive  violence, 
and  shatter  the  bottle  into  a  thousand 
fragments. 

This    experiment    succeeds    best    when 
the  mixture  is  obtained  by  the  electrolysis 
of  hydrochloric  acid.     Collect   the   mixed   gases   in  small  bulbs  of 
thin  glass,  which  are  easily  made  from  glass  tubing.     (Fig.  15). 


In  diffused  light  the  action  is 
prolonged,  and  the  union  takes 
place  without  explosion.  In  dark- 
ness, they  do  not  combine  at  all. 

Exp.  57. — Add  a  solution  of  silver 
nitrate  to  hydrochloric  acid.  (Fig.  16.) 
A  white  precipitate  of  silver  chloride  will 
be  formed.  This  silver  chloride,  exposed 
for  a  short  time  to  the  sunlight,  becomes 
violet,  then  black.  The  silver  chloride 
loses  part  of  its  chlorine. 


FIG,  15. 


FIG.  16. 


to  say  that  this  is  never  reached,  as  a  large  portion  of  the  heat  is  dissipated. 
When  hydrogen  burns  in  air,  the  nitrogen  has  to  be  warmed,  and  the  tem- 
perature attained  is  about  2740°  C.  Here  also,  if  the  blast  of  air  is  too  strong, 
a  less  temperature  will  be  reached;  and  it  is  easily  conceivable  that  a  body, 
by  very  slow  combustion  (rotting),  may  expend  nearly  all  its  available  heat  on 
surrounding  objects. 


44 


CHEMISTRY. 


Light,  therefore,  acts  also  as  a  decomposing  agent. 
The  property  which  light  has  of  darkening  silver 
chloride  and  silver  iodide  has  been  applied  in  pho- 
tography. 

Exp.  58. — Dip  unsized  paper  in  brine  made  of  common  salt, 
and  then  dry  it.  By  means  of  a  light  brush,  cover  one  side  of  this 
with  a  solution  of  silver  nitrate,  and  dry  it  in  a  darkened  room. 
The  surface  of  the  paper  will  be  covered  with  a  film  of  silver 
chloride.  Now  oil  an  ordinary  engraving  so  as  to  render  it  trans- 
lucent. Lay  this  closely  above  the  silvered  side  of  the  paper,  and 
expose  it  to  bright  sunlight  for  ten  minutes.  A  reversed,  or  neg- 
ative, copy  of  the  picture  will  be  found  on  the  paper.  It  may  be 

rendered  permanent  by  soaking  it 
for  a  while  in  a  solution  of  sodium 
hyposulphite,  to  dissolve  the  silver 
chloride  which  has  not  been  changed 
by  the  light,  and  then  by  washing 
the  paper  in  water,  to  remove  the 
hyposulphite.  (See  Exp.  125). 

On  the  other  hand,  light  is 
frequently  evolved  by  chemi- 
cal combination.  This  is,  in 
fact,  the  source  of  most  of  our 
artificial  lights. 

46.  Affinity  is  influenced  by 
electricity.  Frictional  electric- 
ity will  effect  the  combination 
of  some  elements.  We  may 
use  for  this  purpose  a  strong 
glass  tube,  called  an  eudiome- 
ter (Fig.  17),  open  at  one 
end  and  closed  at  the  other. 
Through  the  closed  end  are 
melted  two  platinum  wires,  whose  points  are  separated 
so  that  a  spark  from  a  Leyden  jar  may  pass  between 
them. 


• 


FIG.  17. 


ELECTROLYSIS. 


45 


Exp.  59. — Fill  the  eudiometer  with  mercury:  then  pass  into 
it  a  measured  volume  of  oxygen  and  two  equal  measures  of  hy- 
drogen, taking  care  that  the  mixture  does  not  more  than  half  fill 
the  tuhe.  Close  the  open  end  of  the  tube  by  a  caoutchouc  stopper. 
Now  pass  an  electric  spark  between  the  platinum  points.  A  flame 
will  pass  down  through  the  gas,  showing  that  combination  has 
taken  place.  On  removing  the  caoutchouc  stopper,  the  mercury 
will  rise  and  fill  the  tube. 


o    H 


If  this  experiment  be  modified  by  inclosing  the  closed 
arm  of  the  eudiometer  in  a  larger  tube  which  is  kept 
filled  with  the  vapor  of  amylic  alcohol  (a  liquid  which 
boils  at  132°  C.),  the  water  will  not  condense,  but 
remain  as  steam.  It  will  then  be  found,  on  removing 
the  stopper,  that  the  steam  formed 
by  the  union  of  the  two  gases  fills 
two-thirds  of  the  volume  previ- 
ously occupied  by  the  three  vol- 
umes of  mixed  oxygen  and  hy- 
drogen. 

Therefore,  when  two  volumes 
of  hydrogen  combine  with  one 
volume  of  oxygen,  they  condense 
to  two  volumes  of  aqueous  vapor. 

47.  The  galvanic  current  is  an 

energetic  agent  in  producing  de- 
composition of  compound?.  This 
mode  of  decomposition  is  called 
electrolysis.  FIG.  is. 

Fig.  18  represents  an  apparatus  which  may  be  used  to  show  the 
decomposition  of  water.  It  consists  of  a  glass  vessel  having  two 
corked  openings,  through  which  are  passed  two  wires  terminating 
in  platinum  electrodes.  The  vessel  being  filled  with  water  slightly 
acidulated  with  sulphuric  acid,  two  glass  tubes,  also  filled  with  water, 
are  inverted  over"  the  electrodes,  and  the  outer  wires  are  connected 
with  some  constant  battery.  Four  Grove's  cells  are  sufficient  to 
cause  a  rapid  decomposition  of  the  water. 


46  CHEMISTRY. 

Hydrogen  rises  from  the  negative  electrode,  and  oxy- 
gen from  the  positive.  As  water  absorbs  more  oxygen 
than  hydrogen,  the  gases  evolved  can  not  be  accurately 
measured  until  the  water  is  saturated  with  the  gases. 
It  will  then  be  found  that  exactly  twice  as  great  a  vol- 
ume of  hydrogen  is  evolved  as  of  oxygen.  This  result 
confirms  Exp.  59. 

Other  liquids  may  be  decomposed  by  the  same  ap- 
paratus. Hydrochloric  acid  evolves  hydrogen  at  the 
negative  and  chlorine  at  the  positive  electrode.  After 
the  liquid  is  saturated  with  the  gases,  —  which  will  re- 
quire some  time  if  the  quantity  is  considerable,  —  the 
two  gases  are  evolved  in  equal  volumes;  that  is,  hydro- 
chloric acid  contains  one  volume  of  hydrogen  and  one 
of  chlorine.  If  both  gases  are  collected  in  an  eudiometer 
and  exploded,  it  will  also  be  found  that  they  again  unite, 
without  condensation,  to  two  volumes. 

Fused  metallic  chlorides  yield  the  metal  at  the  nega- 
tive and  the  chlorine  at  the  positive  electrode. 

If,  however,  an  aqueous  solution   be   used,  it  may  act 
on  one  or  both  of  the  constituents  evolved,  and  cause  a 
secondary  action.     An  aqueous  solution  of  iodide   of  po- 
tassiuni  is  easily  decomposed ;  but,  as  soon  as  the  potas- 
sium  is    liberated,   it   decomposes   the 
water,   forming   potassium   oxide,   and 
hydrogen  gas  is  liberated  at  the  nega- 
tive electrode. 


Exp.  60.— Fill  a  U  tube  with  a  solution 
of  sodium  sulphate,  colored  by  an  infusion 
of  red  cabbage,  and  plunge  the  platinum 
electrodes  in  each  arm.  The  fluid  at  the 
negative  electrode  will  be  colored  green,  and 
FIG.  19.  at  the  positive  electrode,  red.  We  have  al- 

ready learned  that  these  changes -in  color  in- 
dicate the  presence  of  an  alkali  and  an  acid. 

The  action  is  somewhat  complex.     To   explain    it    we   may  sup- 
pose the  sodium  sulphate  to  have  the  formula,  Na2SO4.     The  gal- 


GALVANIC  DECOMPOSITION.  47 

vanic  action  breaks  this  up  into  sodium,  Na2,  and  into  SO4.  This 
last  body  has  never  been  obtained  in  a  free  state,  but  it  is  conve- 
nient to  suppose  its  existence  here.  The  sodium  collects  at  the 
negative  pole,  and  the  SO4  at  the  positive.  At  both  poles  a  sec- 
ondary action  takes  place.  A  molecule  of  water  is  decomposed; 
its  hydrogen  unites  with  the  SO4  to  form  H2SO4,  or  sulphuric 
acid;  its  oxygen,  with  the  sodium  to  form  sodium  oxide,  Na2O. 
This  unites  with  another  molecule  of  water,  forming  sodium  hy- 
drate, Na2O,  H2O,  or  2NaHO. 

48,  Since  unlike  electricities  attract   each   other,    the 

bodies  which  collect  at  the  negative  electrode  are  called 
positive,  and  those  which  collect  at  the  positive  electrode 
are  called  negative.  These  terms  are  merely  relative, 
as  chlorine  is  electro-positive  with  reference  to  oxygen 
or  sulphur,  and  electro-negative* with  reference  to  hydro- 
gen and  the  metals.  The  metals  and  their  oxides  are 
generally  electro-positive ;  the  non-metals,  the  semi- 
metals,  and  the  acid  radicals,  generally  electro-negative. 

Exp.  61. — Place  in  a  series  of  test  tubes  solutions  of  the  ni- 
trates of  (1)  lead,  (2)  copper,  (3)  mercury,  (4)  silver.  A  globule 
of  mercury  placed  in  (4)  will  reduce  the  silver,  and  a  nitrate  of 
mercury  will  be  formed.  Similarly,  a  slip  of  bright  copper  in  (3), 
of  iron  in  (2),  or  of  zinc  in  (1),  will  reduce  metallic  mercury, 
copper,  or  lead,  and  form  the  corresponding  nitrates,  thus  exhibit- 
ing a  difference  of  affinity  which  may  be  referred  to  the  difference 
in  electrical  relations.  Zinc  will  reduce  most  metals  from  their 
acid  solutions.  Sodium  amalgam  is  a  still  more  powerful  reducing 
agent  for  the  metals. 

In  many  such  cases  of  reduction,  the  water  of  the  solution  is  first 
decomposed,  its  oxygen  uniting  with  the  zinc  or  the  sodium,  and 
its  nascent  hydrogen  with  the  acid  radical  previously  combined  in 
the  metallic  salt.  Such  reactions  are  secondary,  like  those  described 
in  Exp.  60. 

Generally  speaking,  the  affinities  between  elements 
of  widely  different  electricities,  as  between  the  metals 
and  oxygen  or  chlorine,  are  the  strongest;  but  many 
stable  compounds  are  known  in  which  both  the  elements 
are  reckoned  as  negative;  as,  SO2,  I2O5. 


48  CHEMISTRY. 

The  following  is  a  portion  of  Berzelius's  electro-chem- 
ical series,  in  which  any  element,  counting  from  oxygen, 
is  electro-negative  to  those  that  follow  it,  and  electro- 
positive with  reference  to  those  that  precede  it. 


Oxygen  Caesium 

Sulphur  Potassium 

Nitrogen  Sodium 

Fluorine  Zinc 

Chlorine  Iron 

Bromine  Copper 

Iodine  Silver 

Phosphorus  Mercury 

Carbon  Platinum 

Antimony         Gold 
Hydrogen 
± 

The  galvanic  current  is  maintained  by  a  chemical 
action  which  takes  place  within  the  cell,  proceeding 
from  the  plate  which  is  most  easily  acted  upon  by  the 
fluid  portion  of  the  battery.  Not  only  this,  but  the 
quantity  of  electricity  developed  is  so  related  to  the 
energy  and  amount  of  the  chemical  action,  that  the  pro- 
portions between  them  can  be  expressed  numerically. 

49.  There  is,  therefore,  an  intimate  relation  between 
the  force  of  affinity  and  the  forces  of  heat,  light,  and 
electricity.  Affinity  may  produce  heat,  light,  or  elec- 
tricity. It  may  be  set  in  action  by  either  of  them,  and 
cause  bodies  to  unite,  or  be  so  weakened  that  its  com- 
pounds are  decomposed.  Heat  may  also  generate  elec- 
tricity, and  electricity  be  made  to  evolve  heat  and  light. 
For  these  reasons  these  forces  are  called  the  correlative 
forces. 

Finally,  there  are  so  many  cases  in  which  the  disap- 
pearance of  one  of  these  forces  is  marked  by  the  evo- 
lution of  another  in  numerical  proportions,  that  we  are 


CORRELATIVE  FORCES.  49 

justified  in  the  conclusion  that  these  forces  are  converti- 
ble the  one  into  the  other;  that  affinity,  for  instance, 
may  reappear  as  heat,  light,  or  electricity,  singly  or 
simultaneously.  If  this  be  true,  we  are  not  to  suppose 
that  when  we  can  no  longer  trace  the  action  of  a  force, 
it  has  been  annihilated,  but  that  it  has  changed  to  some 
other  form  of  force.  Force  is,  therefore,  indestructible. 
The  correlative  forces  are  all  thought  to  be  modes  of 
motion  impressed  upon  the  ultimate  particles  of  matter 
in  bodies.  The  difference  in  the  mode  of  motion  deter- 
mines whether  heat,  light,  electricity,  or  affinity  is  pro- 
duced. Affinity  seems  to  stand  in  closer  relation  to 
electricity  than  to  either  of  the  other  forces. 

Recapitulation, 

The  characteristics  of  chemical  affinity: 

It  varies  with  the  kind  of  matter; 

with  the  relative  mass  of  matter; 

is  strongest  in  the  nascent  state  of  matter; 

It  varies  with  the  state  of  cohesion ; 

with  the  solubility  of  the  product; 
with  the  volatility  of  the  product. 

A  fluid  state  necessary  to  effect  combination. 

It  is  influenced  by  adhesion; 

by  the  state  of  division  of  matter. 

Surface  action  induces  combination. 

It  is  influenced  by  heat, 

so  as  to  effect  combination; 
so  as  to  effect  decomposition. 

It  is  influenced  by  light, 

so  as  to  effect  combination; 
so  as  to  effect  decomposition. 

It  is  influenced  by  electricity, 

so  as  to  effect  combination; 
so  as  to  effect  decomposition. 

Correlatively:    It  may  produce  heat,  light,  and  electricity. 
Chem. — 4t 


CHAPTER    III.* 


CHEMICAL    PHILOSOPHY    AND    NOMENCLATURE. 

50.  The  facts  of  chemistry  arc  established   by  experi- 
ment, and  are  capable  of  being  reproduced.     They  find 
a  practical   application   in   the   arts,  which  is  altogether 
independent   of  any  explanation   that  may  be   made   of 
them.     When,    however,    we    attempt    to    reason    iipou 
these   facts,   to   classify  them,   to   interpret  them,  we  at 
once  begin   to   form   theories.     A  theory  which  renders 
u  reasonable  explanation  of  a  great  number  of  facts  is 
useful   (1)   because   it  enables   us   to  group  them  into  a 
system,  and   (2)  because   it  often    leads  to   new  experi- 
ments and  to  the  discovery  of  other  facts. 

We  are  liable  to  three  errors:  (1)  we  may  assume  that  to  be  a 
fact  which  has  no  existence;  or  (2)  we  may  sometimes  mistake  a 
phenomenon,  so  as  to  imagine  that  to  be  a  cause  which  is  only  an 
effect  of  some  unknown  cause;  or,  finally,  (3)  we  may  become  so 
accustomed  to  the  language  of  theory  as  to  mistake  its  definitions 
for  facts.  Once  assured  of  our  facts,  we  may  be  certain  that  they 
are  immutable.  Nevertheless,  it  has  often  happened  that  statements 
which  have  been  accepted  as  facts  have  been  rejected  because  they 
have  been  found  to  be  false;  and  that  one  theory  has  been  dis- 
placed by  another  which  interprets  a  greater  number  of  facts. 

51.  We  know  nothing    of  the    manner   in  which   the 
ultimate  particles  of  matter  are   arranged   together :    we 
believe  that  they  are  arranged  in  accordance  with  certain 
theories  which  we  shall  now  proceed  to  develop. 

All  masses  of  matter  may  be  subdivided  into  very 
small  particles ;  but  it  is  probable  that  there  is  a  limit 

*  To  TEACHERS.— The  author  advises  that  young  students  in  chemistry  should 
study,  on  the  advance,  only  so  much  of  this  chapter  as  is  necessary  to  accept  the 
fact  of  atomicity,  and  the  notation  and  nomenclature  of  compounds.  The  full 
discussion  of  chemical  philosophy  may  be  deferred  until  the  class  has  reached 
Chapter  XI.  Mature  students  will  find  it  best  to  mastec  the  subject  at  this 
point,  where  it  logically  belongs.  It  is  not  exceptionally  difficult. 
(50) 


ATOMIC  THEORY.  51 

to  this  subdivision,  and  that  all  bodies  are  made  up  of 
particles  so  infinitesimally  small  that  they  are  inappre- 
ciable to  our  senses.  By  the  terms  of  this  theory, 

A  molecule  is  the  smallest  particle  of  matter  capable 
of  existing  in  the  free  state: 

An  atom  is  the  smallest  particle  of  matter  that  is  ca- 
pable of  entering  into  or  existing  in  a  state  of  chemical 
combination. 

If  we  subdivide  hydrochloric  acid,  the  least  particle  that  we  can 
obtain,  without  destroying  the  identity  of  the  acid,  is  a  molecule; 
but  we  know  that  this  molecule  contains  still  smaller  particles  of 
hydrogen  and  chlorine.  Compound  bodies  contain  the  atoms  of 
different  elements,  united  to  form  compound  molecules;  as,  HC1. 
"We  suppose,  also,  that  the  atoms  of  the  same  element  may  unite 
to  form  elementary  molecules;  as,  H2  or  C12. 

52,  It  is  also  believed  (1)  that  the  atoms  of  the  same 
element  are  exactly  alike,  and  that  they  have  a  definite 
size,  shape,  and  weight ;  (2)  that  the  atoms  of  different 
elements  are  always  unlike,  differing  in  weight  and, 
perhaps,  in  form;  and  (3)  that  equal  volumes  of  all 
aeriform  bodies  contain,  at  the  same  temperature  and 
pressure,  an  equal  number  of  molecules.*  (4)  It  also 
naturally  follows  that  one  molecule  of  any  aeriform  body 
must  occupy  a  certain  definite  space,  which  is  called  its 
molecular  volume,  and  that  all  molecular  volumes  are  equal. 

Hereafter  it  will  be  assumed  that  all  gases  are  measured  when 
at  the  temperature  of  the  freezing  point  of  water,  and  under  the 
pressure  of  one  atmosphere.  These  are  called  the  normal  condi- 
tions of  temperature  and  pressure. 

The  following  table  gives  the  weight  in  grammes  of  11.2  litres 
of  the  following  elements,  when  in  the  aeriform  state,  at  the  normal 
temperature  and  pressure: 

Hydrogen,  1.  Oxygen,     16.  Phosphorus,  62. 

Chlorine,   35.5  Sulphur,     32.  Arsenic,       150. 

Bromine,   80.  Selenium,  79.5  Mercury,     100. 

Iodine,      127.  Nitrogen,  14.  Cadmium,      56. 

*  This  is  known  as  Avogadro's  Law. 


52  CHEMJSTJ!  V. 

These  numbers  are  also  the  rclatirc  irdf/htfi  of  equal  volumes, 
whether  those  volumes  are  measurable  or  infinitesimal.  The  stu- 
dent must  always  remember  that  a  molecular  volume  or  an  atomic 
weight  is  a  definite  quantity,  although  very  small. 

53.  The  absolute  weight  or  the  volume  of  any  atom  is 
not  certainly  known.*  The  combining  numbers  given  on 
pp.  12  and  13  express  the  relative  weights  of  the  atoms, 
and  are  called  the  atomic  weights.  These  numbers  have 
been  obtained  by  several  extended  series  of  observations. 
The  principal  considerations  that  have  led  to  their  adop- 
tion are  the  following : 

Hydrogen  is  the  lightest  element  known.  We  may 
therefore  take  it  as  the  unit  by  which  other  substances 
may  be  compared;  that  is,  as  the  standard  unit  (1)  for 
the  specific  gravity  of  gases ;  (2)  for  atomic  weight ; 

(3)  for  molecular  volume;  and,  as  we  shall  see  hereafter, 

(4)  for  the  unit  of  combining  power. 

We  have  learned  (p.  40)  that  two  volumes  of  hydro- 
chloric acid  gas  contain  one  volume  of  hydrogen  and 
one  of  chlorine.  Since  all  molecular  volumes  are  equal, 
two  molecular  volumes  of  hydrochloric  acid  gas  must 
contain  one  molecular  volume  of  hydrogen  and  one 


*  Physicists  have  carried  the  doctrine  of  molecules  further.  They  find  that 
most  of  the  phenomena  exhibited  by  gases,  such  as  their  elastic  force,  can  be 
satisfactorily  explained  on  the  assumption  that  these  bodies  consist  of  perfectly 
elastic  particles,  which  are  perpetually  colliding  against  each  other,  and  against 
the  sides  of  the  vessel  which  contains  them  They  have  even  gone  so  far  as  to 
make  an  attempt  to  measure  the  size  and  mass  of  the  molecules,  the  distances 
between  them,  and  the  rate  of  their  motion.  The  following  are  Maxwell's 
results.  Two  hundred  million  hydrogen  molecules  in  a  row  would  measure 
little  more  than  one  centimetre.  In  a  cubic  centimetre  of  any  gas  under  the 
normal  conditions  of  temperature  and  pressure,  there  are  19.000,00a,000,000,000,000 
molecules.  The  velocity  of  the  hydrogen  molecule  is  1,843  metres  per  second. 
The  mass  of  a  molecule  of  hydrogen  is  4(5  ten-million,  million,  million  millionths 
of  a  gramme.  The  masses  of  the  molecules  of  all  gases  are  as  their  atomic 
weights ;  hence,  the  velocity  of  gases  will  be  inversely  proportional  to  the  square 
roots  of  their  atomic  weights.  The  spaces  which  separate  the  molecules  are 
much  larger  than  the  molecules  themselves.  Reckoned  in  hundred  billionths 
of  a  metre,  a  molecule  of  hydrogen  would  have  a  diameter  of  58,  while  the  mean 
path  which  it  describes  is  0,650,  and  the  number  of  collisions  it  encounters  per 
second  amount  to  17,750  millions. 


MOLECULAR    VOLUMES.  53 

of  chlorine.  On  analysis,  we  find  that  one  molecular 
volume  of  hydrochloric  acid  gas  yields  one  atom  of 
chlorine  and  one  atom  of  hydrogen.  The  two  molecular 
volumes  of  the  acid  gas,  therefore,  contain  two  atoms 
of  hydrogen  and  two  of  chlorine.  A  molecule  of  hydro- 
gen must,  therefore,  contain  two  atoms,  and  a  molecule 
of  chlorine  two  atoms.  Therefore,  if  the  atomic  weight 
of  hydrogen  be  assumed  as  unity,  its  molecular  weight 
will  be  2,  and  its  molecular  volume  also  2. 

54.  Since  all  molecular  volumes  are  equal,  the  mole- 
cular   volume    of   any    aeriform    substance    must    be    2. 
The   density   of  aeriform  bodies    is   the   relative  weight 
of  one  volume ;  hence,  the  molecular  weight  of  any  aeri- 
form body  must  be  double    its   density.     The  molecular 
weights  of  the  elements  previously  named  are : 

Hydrogen,    2.  Nitrogen,     28.  Phosphorus,  124. 

Chlorine,     71.  Oxygen,       32.  Arsenic,         300. 

Bromine,   1GO.  Sulphur,      64.  Mercury,       200. 

Iodine,       254.  Selenium,  159.  Cadmium,     112. 

If  all  the  elementary  molecules  had  the  same  number 
of  atoms  as  the  hydrogen  molecule,  the  atomic  weights 
of  the  elements  would  be  identical  with  their  densities. 
This  is  the  case  with  most  of  the  elements  that  can  be 
obtained  in  the  aeriform  state.  In  all  cases  the  mole- 
cular weight  of  an  element  is  equal  to  the  product  of 
its  atomic  weight  by  the  number  of  atoms  in  one  ele- 
mentary molecule.  Hence,  if  we  know  any  two  of  these 
quantities,  we  can  find  the  other  by  a  simple  calculation. 

55.  The  atomic  weight  of  any  element  is  obtained  by 
comparing   the    results    of  the    analysis    of  many    com- 
pounds of  that  element.     When  the  compound  is  a  gas. 
the  density  is   obtained   by  direct   experiment,   and  the 
relative   proportions    of  its    constituents   are    easily   de- 
termined. 


54 


CHEMISTRY. 


Two  volumes   of  each  of  the  following  compounds  of 
hydrogen  are  found  to  yield  these  results : 


WEIGHTS 

OF  TWO 

DEN- 

PROPORTIONS 

PROPORTIONS 

FOR- 

/GLUMES 

SITY 

NAME  OF  COMPOUND 

BY    WEIGHT 

BY    VOLUME 

MULAE 

36.5 

18.25 

Hydrochloric  acid. 

H,  1  -f  Cl,  35.5 

H,    1   -f  Cl,  1 

HC1 

18. 

9. 

Perfect  steam. 

H,  1  4-  O,     8. 

H,  2  -f  0,  1 

H20 

17. 

8.5 

Ammonia. 

H,  1  4-  N,    4.7 

H,  3  4-  N,  1 

H3N 

16. 

8. 

Marsh  gas. 

H,  1  -f  C,     3. 

H,  4  +  C,  1 

H4C 

If  we  consider  only  the  weights  which  unite  with  one  part  of 
hydrogen,  the  atomic  weight  of  chlorine  is  35.5;  of  oxygen,  8;  of 
nitrogen,  4.7;  and  of  qarbon,  3. 

The  molecular  weight  of  each  of  these  compounds  is  equal  to 
the  weight  of  two  volumes.  The  molecular  weight  is  also  equal  to 
the  sum  of  the  atomic  weights  of  its  constituents.  If  these  two  do 
not  agree,  the  atomic  weights  assigned  are  incorrect. 

The  molecular  weight  of  hydrochloric  acid  is  36.5:  this  is  also 
the  sum  (35.5  -f-  1)  of  the  combining  weights  of  chlorine  and  hy- 
drogen. Therefore,  35.5  is  the  atomic  weight  of  chlorine. 

The  molecular  weight  of  steam  is  18;  but  the  sum  (l-f-8)  of 
the  combining  weights  is  half  of  this;  hence,  one  molecule  of  steam 
must  contain  2  parts  of  hydrogen  and  16  of  oxygen. 

So,  also,  17  parts,  by  weight,  of  ammonia  must  contain  3  parts 
of  hydrogen  and  14  of  nitrogen;  and  16  parts,  by  weight,  of  marsh 
gas  must  contain  4  parts  of  hydrogen  and  12  of  carbon. 

As  we  know  of  no  hydrogen  compounds  in  which 
chlorine,  oxygen,  nitrogen,  and  carbon  unite  in  less 
proportion  than  35.5,  16,  14,  and  12,  these  numbers  are 
adopted  as  the  atomic  weights  of  these  elements. 

56  a.  The  atomic  weights  of  those  elements  which  do  not 
form  aeriform  compounds  with  hydrogen,  are  determined 
by  careful  analyses  of  their  compounds  with  chlorine 
or  with  some  element  whose  atomic  weight  is  known. 

We  are  aided  in  determining  what  number  is  most  likely  to  rep- 
resent correctly  the  atomic  weight  of  these  elements,  (1)  by  means  of 
the  vapor  density  of  their  aeriform  compounds,  if  they  have  any. 

(2)  By  the  fact  that  the  similar  salts  (chlorides,  sulphates,  etc.), 
of  very  many  elements,  may  be  arranged  in  groups  which  have  the 
same  crystalline  form.  Such  substances  are  said  to  be  isomvrph&us ; 


ATOMIC  WEIGHTS.  55 

as,  for  example,  Mg,  Zn,  Cd.  Now,  we  know  the  molecular  weight  of 
the  cadmium  salts  by  means  of  their  vapor  densities,  and  it  is  fair  to 
suppose  that  the  others  have  the  same  molecular  structure  and  may 
be  represented  by  analogous  formulae. 

(3)  A  more  general  aid  in  determining  the  atomic  weight  of  an 
element  is  by  means  of  its  specific  heat.  The  specific  heat  of  a 
body  is  the  fraction  which  expresses  the  amount  of  heat  required 
to  raise  a  unit  weight  of  the  substance  as  compared  with  that  re- 
quired to  raise  an  equal  weight  of  water  from  0°  C.  to  1°  C.  It  is 
found  that  the  product  of  the  atomic  weights  by  the  specific  heats 
of  the  several  elements  is  a  constant  quantity,  which  is  called  the 
specific  heat  of  atoms.  The  mean  value  of  this  product  is  6.34,  and 
any  small  deviation  from  it  is  thought  to  result  from  the  unavoid- 
able errors  of  experiment. 

These  relations  are  shown  in  the  following  table: 

SPECIFIC  ATOMIC 

HEAT.  WEIGHT. 

Sodium,  0.29340  X    23  =  6.75 

Sulphur,  0.20259  X    32  =  6.48 

Arsenic,  0.08140  X    75  =  6.11 

Phosphorus,  0.18870  X    31  =  5.85 

Mercury,  0.03192  X  200  =  6.38 

Cadmium,  0.05669  X  112  =  6.35 

Zinc,  0.09555  X    65  =  6.21 

Carbon,  0.45900  X    12  =  5.51 

Silicon,  0.20300  X    28  =  5.68 

Average, 6.34 

56  b.  If  we  divide  the  molecular  weights  of  the  ele- 
ments by  the  atomic  weights,  we  shall  find  the  number 
of  atoms  in  each  molecule  in  the  aeriform  state. 

Mercury,  zinc,  and  cadmium  have  each  one  atom  in  a  molecule. 
Their  vapor  densities  are  half  their  atomic  weights,  and  their  atomic 
volumes  are  only  half  those  of  hydrogen. 

Phosphorus  and  arsenic  have  each  four  atoms  in  a  molecule. 
Their  vapor  densities  are  double  their  atomic  weights,  and  their 
atomic  volumes  are  only  half  those  of  hydrogen. 

Most  of  the  other  elements  are  supposed  to  contain  two  atoms  in 
each  molecule.  Their  vapor  densities  are  equal  to  their  atomic 
weights,  and  their  molecular  volume  is  equal  to  that  of  hydrogen. 


5f>  CHEMISTRY. 

57.  If  these  considerations  are  accepted,  we  must  rep- 
resent hydrochloric   acid   by   the   formula,   IIC1 ;    water, 
by  H2O;    ammonia,  by  H3N ;  and  marsh  gas,  by  H4C. 

Each  separate  symbol  represents  (1)  one  atomic  vol- 
ume, (2)  one  atomic  weight,  and  (3)  the  specific  gravity 
of  each  element  in  the  aeriform  state  referred  to  hydro- 
gen as  unity.  (4)  The  numbers  below  each  letter  show 
how  many  times  the  atom  is  taken  to  form  the  com- 
pound molecule. 

Each  formula  represents  (1)  one  compound  molecule: 
its  molecular  weight  is  the  sum  of  the  atomic  weights 
of  its  constituents.  (2)  It  also  represents  two  volumes, 
and  therefore  its  specific  gravity,  in  the  aeriform  state, 
is  half  the  molecular  weight. 

58.  These  formulae   aiv  called  typical  formulas,  because 
they  may  be  severally  taken  as  types  or  examples  of  a 
large  number  of  compounds  having  a  similar  molecular 
structure.     Thus,  we  may  have: 


Hydrochloric 

Acid 

Water 

Ammonia 

Marsh  Gas 

HC1 

H20 

H3N 

H4C 

Hydrobromic 
Acid 

Hydrogen 
Sulphide 

Hydrogen 
Phosphide 

Hydrogen 
SHioide 

HBr 

H,S 

H3P 

H4Si 

Hydriodie 
Acid 

Hydrogen 
Selenide 

Hydrogen 
Arsenide 

HI 

H2Se 

H3As 

59.  We  can  not  fail  to  notice  that  these  groups  are 
distinguished  by  the  number  of  atoms  of  hydrogen 
which  combine  with  one  atom  of  the  other  element. 
Chlorine  has  a  combining  power  sufficient  to  fix  one 
atom  of  hydrogen ;  oxygen  has  a  combining  power  suf- 
ficient to  fix  two  atoms  of  hydrogen;  nitrogen  has  a 


ATOMICITY.  57 

Combining  power  of  3;  carbon,  of  4.  Atoms  which 
have  an  equal  combining  power  are  said  to  be  equiva- 
lent, or  to  have  the  same  atomicity ;  that  is,  they  may 
replace  each  other,  atom  for  atom. 

Thus,  if  we  decompose  hydriodie  acid  by  chlorine,  we  may  rep- 
resent the  reaction,  HI  -j-  Cl  =  HC1  -f-  I.  Chlorine  and  hydrogen 
have  each  the  same  combining  power.  The  metals  —  potassium, 
sodium,  and  silver  —  form  compounds  which  contain  one  atom  of 
chlorine.  They  displace  one  atom  of  hydrogen  in  hydrochloric 
acid,  and  are  equivalent  to  it:  HC1  -f-  Na  =  NaCl  -f  IT. 

On  the  other  hand,  if  we  decompose  water  by  chlorine,  the  re- 
action is,  H2O  -f  Cl,  =  2HC1  -f-  O.  Two  atoms  of  chlorine  are  re- 
quired to  displace  one  atom  of  oxygen ;  hence,  the  oxygen  atom 
has  twice  the  combining  power  of  chlorine,  or  can  fix  two  atoms 
of  hydrogen.  So,  also,  one  atom  of  sulphur,  calcium,  or  zinc 
combines  with  two  atoms  of  chlorine  or  with  one  of  oxygen, 
and  has  double  the  combining  power  of  hydrogen,  or  an  atom- 
icity of  2. 

60.  All  the  elements  may  be  arranged  in  seven  groups, 
according   as    they    combine    with    1,   3,   5,   7   atoms    or 
2,   4,   (3    atoms    of  hydrogen    or    of  chlorine.     The    ele- 
ments which  make  up  these  groups  are  called : 

Monads  or  univalent,     whose  atomicity  ==  1  as  H/ 

Dyads  or  bivalent,  "  "  -2,  as  O/x 

Triads  or  trivalent,  =  3  as  B"' 

Tetrads  or  quadrivalent,    "  =  4  as  C/r 

Pentads  or  quinquivalent,  "  "  =  5  as  N  v 

Hexads  or  sexivalent,          "  "  =6  as  Sr/ 

Heptads  or  septivalent,      "  "  =7  as  Clr// 

61.  The  equivalence  or  atomicity  of  an  atom  is  rep- 
resented   by  accent    marks    or  Roman   numerals    placed 
above    the    symbol.     These    marks  do   not    multiply  the 
atoms,  and    should    not   be  confounded  with  the  figures 
placed  below  the  symbols. 

The  atomicity  is  sometimes  expressed  graphically  by  lines  called 


58 


CHEMISTRY. 


bonds  radiating  from   a   symbol,  or  from  some  figure  which  repre- 
sents an  atom.     The  following  are  examples: 


MOXADS         DYADS         TRIADS         TETRADS         PENTADS         HEXADS         HEPTADS 
HI  ()II  BTII  CIV  NV  gVI.  C1VII 


H-      -O-       -B-      -C  - 


H 
H 


0 
O 

n 


B 


B 

m 


N 
N" 


Cl 
Cl 


62.  The  atomicities  of  all  of  the  elements  have  not 
been  experimentally  determined,  and  are  open  to  re- 
vision. There  are  also  apparent  variations  in  the  equiv- 
alency of  many  elements,  which  are  difficult  of  explana- 
tion. Thus,  nitrogen  is  trivalent  in  ammonia,  NH3,  and 
quinquivalent  in  ammonium  chloride,  NH4C1.  Chlorine 
is  usually  regarded  as  a  monad  element,  but  it  appears 
also  to  act  as  a  heptad.  So,  also,  iron  is  variously  classed 
a  bivalent,  quadrivalent,  and  sexivalent  element. 

Generally,  but  not  always,  the  atomicity  assigned  to 
an  element  is  that  derived  from  its  highest  compound 
with  monad  elements,  and  any  lower  compound  is  said 
to  be  unsaturated,  or  that  the  element  has  one  or  more 
of  its  bonds  unsatisfied.  Such  unsaturated  compounds 
are  frequently  unstable,  and  tend  to  form  the  higher, 
saturated  compound.  Thus,  in  ferrous  chloride,  Fe/7Cl2, 
the  iron  is  apparently  bivalent,  but  on  exposure  to  the 
air  it  forms  ferric  compounds  which  are  either  quadri- 
valent or  sexivalent. 


| 
FeE01 


or  Fe'FC 


or  Fer/2Cle 


PERISSADS  AND  ARTIADS. 


59 


We  find,  however,  that  the  same  element  almost 
always  exhibits  a  valency  which  may  be  represented 
either  by  an  odd  or  by  an  even  number.  Those  ele- 
ments whose  valency  can  be  represented  by  1,  3,  5,  or 
7,  are  called  perissads ;  those  whose  valency  is  2,  4,  6, 
or  8,  are  called  artiads.  It  is  also  noticeable  that  the 
sum  of  the  bonds,  in  a  stable,  saturated  molecule,  is 
always  an  even  number. 

Although  there  are  many  apparent  contradictions  and 
unexplained  anomalies  in  the  doctrine  of  atomicity,  it 
bids  fair  to  be  of  immense  importance  in  theoretical 
chemistry. 

The  following  table  gives  the  atomicities  usually  as- 
signed, and  also  groups  the  elements  in  accordance 
with  their  more  striking  properties. 


ELEMENT. 

Hydrogen 

Fluorine 
Chlorine 
Bromine 
Iodine 


Lithium 

Sodium 

Potassium 

Rubidium 

Caesium 

Silver 


TABLE   OF   THE   ELEMENTS. 

PERISSADS. 
MONADS. 

SYMBOL. 

H 

F 
Cl 
Br 
I 

Li 

Na 
K 
Rb 
Cs 

Ag 


TRIADS. 

roMic 

EIGHT. 

ELEMENT.                    SYMBOL. 

1. 

Boron                    B 

19. 

Indium                 In 

35.5 

Gold                     Au 

80. 

Thallium              Tl 

127. 

PENTADS. 

7. 

Nitrogen              N 

23. 

Phosphorus          P 

39.1 

Vanadium            V 

85.4 

Arsenic                 As 

133. 

Antimony            Sb 

Bismuth               Bi 

108. 

Niobium               Cb 

Tantalum             Ta 

ATOMIC 
WEIGHT. 

11. 

113.4 

197. 

204. 


14. 

31. 

51.2 

75. 
122. 
210. 

94. 
182. 


60 


CHEMISTRY. 


ELEMENT. 

Oxygen 

Calcium 

Strontium 

Barium 


SYMBOL. 

o 

Ca 
Sr 
Ba 


Magnesium  Mg 

Zinc  Zn 

Cadmium  Cd 


Carbon 
Silicon 
Titanium 
Tin 

Aluminium 

Gallium 

Zirconium 

Cobalt 

Nickel 

Cerium 

Uranium 

Lead 

Palladium 
Platinum 
Rhodium 
Iridium 


TETRADS. 
C 

Si 
Ti 

Sn 

Al 
Ga. 
Zr 

Co 
Ni 
Ce 
U 
Pb 

Pd 
Pt 
Rh 
Ir 


ARTIADS. 

DYADS. 

TOM  1C 

EIGHT. 

ELEMENT.                   SYMBOL. 

16. 

Copper                  Cu 

40. 

Mercury                Hg 
Glucinum             G 

87.6 

Thorinum             Th 

137. 

Yttrium                 Y 

Lanthanum           La 

24. 

Didymium            D 

65.2 

Erbium                 E 

112. 

Terbium               Tr 

HEXADS. 

12. 

Ruthenium           Ku 

28. 

Osmium                 Os 

50. 

118. 

Molybdenum       Mo 

27.4 

Tungsten              W 

69.9 
89.6 

Sulpliur                S 
Selenium               Se 

58.8 

Tellurium             Te 

58.8 
92. 
120. 
207. 

Chromium            Cr 
Manganese           Mn 
Iron                       Fe 

106. 
197.4 
104.4 

NOTE.  —  This   list   is 
"  Watt's   Dictionary   of 
The  atomic  weights  dc 
accord  with    those   giv< 

198. 

and  13. 

ATOMIC 
WEIGHT. 

63.4 
200. 

9.4 

57.9 

61.6 

93.6 

95. 

112.6 

148.5 


104.4 
199.2 

96. 
184. 

32. 
79.4 
128. 

52.2 

55. 

56. 

from 


63.  We  may  suppose  that  the  elementary  molecules 
consist  of  two  atoms  whose  bonds  mutually  satisfy  each 
other,  graphically  represented  thus: 

H  —  H,    Hydrogen.        O  =  =  O,    Oxygen.         NEEN,    Nitrogen. 

In  compounds,  any  atom  may  have  its  bonds  satisfied 
by  another  atom  having  an  equal  atomicity ;  or  by  sev- 


RADICALS.  61 

eral  atoms,  the  sum  of  whose  bonds  is  equal  to  that  of 
the  first;  thus,  a  dyad  may  be  saturated  by  two  monad 
atoms  or  by  one  dyad  atom;  a  triad  by  a  triad,  by  three 
monads,  or  by  one  monad  plus  one  dyad,  etc.  Thus, 
we  may  represent  graphically: 


Mercuric  oxide,          Hg//nO// 
Water,  H'-O"-H' 

Sodium  hydrate,         Na'-O"-H 
Carbonic  anhydride,  Q"=CIV=< 


II 


Ammonia,       11'-  Nx//-  H' 

W 
Marsh  gas,      H'- C"- H' 


II 


64.  In  compounds,  u  portion  of  the  bonds  of  a  multiv- 
alent  atom  may  be  satisfied  by  another  atom  of  the 
same  element.  Examples  of  this  may  be  represented 
graphically,  thus : 

Hg" 


Mercurous  oxide, 


Mercurous  chloride, 


Hg" 
Hg"-Cl' 


Hg"-  CY 


Ferrous  chloride, 


Ferric  chloride, 


65.  The  theory  of  atomicities  has  received  an  impor- 
tant extension  in  the  doctrine  of  radicals. 

Suppose  an  atom  of  hydrogen  were  removed  from  the 
saturated  molecules,  HC1,  H2O,  H3N,  H4C :  there  would 
remain,  01,  HO,  H2N,  H3C.  These  residues  are  evi- 
dently unsaturated,  and  are  able  to  combine  with  an 
atom  of  hydrogen  to  reproduce  the  original  compound, 
or  with  any  other  monad  to  form  such  compounds  as, 
C12,  KC1,  KHO,  KH2N,  H3C1C.  Such  unsaturated 
residues,  or  groups  of  atoms,  are  called  radicals. 

Compound  radicals  act  precisely  like  the  elements:  they  do  not 
generally  exist  in  a  free  state  in  nature,  but  sometimes  may  com- 
bine with  a  similar  group  to  form  saturated  molecules.  If  but  one 
hydrogen  atom  is  removed,  the  radical  is  univalent;  if  two,  biva- 
lent; if  three,  trivalent;  and  so,  generally,  the  equivalence  of  the 
radical  is  the  number  of  unsatisfied  bonds. 


62 


CHEMISTRY. 


From  marsh  gas  \ve  may  derive  four  radicals,  and 
obtain  by  their  union  with  elementary  atoms,  or  with 
other  radicals,  a  great  number  of  compounds.  Thus, 
we  may  have  from  H4C,  —  marsh  gas,  a  saturated 
compound. 


FORMING  COMPOUNDS   WITH 

RADICALS. 

NAME. 

CHLORINE. 

OTHER  RADICALS. 

(CH3)'   univalent 
(CH2)"  bivalent 
(OH)'"  trivalent 

Methyl 
Methylene 
Formyl 

CH3C1,  methyl 
chloride 
CH2C12,  methy- 
lene  chloride. 
CHC13,     chloro- 
form. 

(CH3)2,    free 
methyl. 
(CH2)202,  di- 
oxymethylene, 
CHO,  O,  C2H5, 
formic  ether. 

(C)/r       quadrivalent 

Carbon 

CC14,  tetra-chlo- 
ride  of  carbon. 

CH4,  marsh  gas. 

66.  The  term  radical  is  further  applied  to  any  group 
of  atoms  which  is  common  to  a  series  of  allied  com- 
pounds. We  may  thus  have  an  almost  infinite  series 
of  radicals,  which  are  for  the  most  part  purely  hypo- 
thetical, and  which  we  do  not  expect  to  obtain  in  an 
isolated  form.  Among  those  recognized  in  inorganic 
chemistry,  that  have  received  names,  are  the  following: 


(HO)/      hydroxyl. 
(HS)'       hydrosulphuryl. 
(H4N)/   ammonium. 
(H2N)'   amidogen. 
(CN)'      cyanogen. 


(NO,)'  nitryl. 

(NO)'  nitrosyl. 

(S02)"  sulphuryl. 

(CO)"  carbonyl. 

(PO)/X/  phosphoryl. 


The  names  of  all  compound  radicals,  except  the  three 
given  above,  end  in  yl.  The  radicals  recognized  in  or- 
ganic chemistry  are  so  numerous  that  this  branch  of 
the  science  has  been  called  the  chemistry  of  compound 
radicals. 

67.  The  nomenclature  and  notation  of  compounds  are 
at  present  in  a  confused  state,  This  arises  from  the 


NOTATION  OF  COMPOUNDS.  63 

fact  that  two  principal  systems  are  in  common  use :  the 
older,  devised  by  Lavoisier  and  Berzelius,  is  based 
mainly  on  the .  structure  of  the  oxygen  compounds,  and 
regards  all  ternary  oxides  as  made  up  of  two  groups 
of  binary  oxides;  as,  BaO  -f  SO3  =  BaO,  SO3.  This  is 
called  the  dualistic  system. 

The  newer  system  regards  every  molecule  as  a  unit; 
as,  BaSO4,  and  is  called  the  unitary  or  molecular  system. 

68.  Formulae   are   called   empirical   when   they   simply 
express  the  results  of  analysis  in  atomic  symbols,  with- 
out  endeavoring   to    denote    the    manner   in    which  the 
atoms  are  united ;  and  rational,  if  they  endeavor  to  rep- 
resent the  manner  in  which  the  atoms  are  grouped  to- 
gether in  a  compound.     There  can  be  but  one  empirical 
formula  of  a  substance,  but  there   may  be  as  many  ra- 
tional formulae  of  any  compound  as  there   are   different 
views  respecting  its  molecular  structure.     The  principal 
of  these   rational   formulae  are :    (1)  the  dualistic,  repre- 
senting the  theory  of  Berzelius;  (2)  the  typical,  in  which 
the   grouping  is  referred    to    representative    compounds 
called  types;  such  as,  II2,  HC1,  H2O,  H3N,  H4C;   and 
(3)  the  structural,  which  are  an  extension  of  the  typical 
by  including  the  compound  radicals.     All   of  these   for- 
mula? are  useful ;   but   the    student   must   bear   in   mind 
that   no   one   of  them   represents  the  actual  position  or 
grouping  of  the  atoms  in  a  complex  formula  with  abso- 
lute certainty.     Its  terms  are  thus  defined : 

69.  According  to  the  dualistic  theory,  all  binary  oxides 
may  be  classed  in  three  groups :  bases,  indifferent  bodies, 
and  acids. 

Bases  are  electro-positive  binaries,  which  are  formed  by  the  union 
of  oxygen  with  a  metal.  Acids  are  electro-negative  binaries,  which 
are  generally  formed  by  the  union  of  oxygen  with  a  non-metal. 
The  soluble  acids  have  a  sour  taste,  and  redden  litmus  paper;  the 
goluble  bases  have  frequently  an  acrid  taste,  and  restore  the  color 


64 


CHEMISTRY. 


of  reddened  litmus  paper.  The  strongest  bases  are  called  the  alka- 
lies: they  are  the  oxides  of  the  potassium  group. 

The  two  groups  are  further  characterized  by  the  fact  that  they 
combine  together  to  form  ternary  compounds  called  salts.  Thus, 
BaO  is  a  base,  barium  oxide;  SO3  is  an  acid,  sulphuric  acid.  Both 
these  may  be  obtained  in  an  isolated  form.  If  they  are  heated 
together  they  form  BaO,  SO3,  which  is  a  salt  called  barium  sulphate. 

An  indifferent  body  is  one  that  either  (1)  will  combine  with  no 
other,  or  (2)  that  sometimes  plays  the  part  of  a  base  and  sometimes 
that  of  an  acid.  Water  is  an  indifferent  body:  it  combines  with 
barium  oxide  to  form  barium  hydrate,  BaO,  H2O;  it  also  combines 
with  sulphuric  anhydride  to  form  hydric  sulphate,  H2O,  SO3. 

70.  The  later  theories  use  the  same  terms,  but  with 
a  different  meaning.  Oxides  that  do  not  contain  hydro- 
gen are  called  anltydrides.  The  metallic  oxides,  like 
K9O,  CaO,  HgO,  are  called  basic  anhydride*;  and  the 


non-metallic    oxides,    like    SO 


3, 


are    called    acid 


anhydrides.     These    are    named    like   other    binary   com- 
pounds : 


ACID   ANHYDRIDES. 

Sulphurous  anhydride. 
Sulphuric  anhydride. 
Hypochlorous  anhydride. 
Chlorous  anhydride. 
Nitrous  anhydride. 
Nitric  anhydride. 
lodic  anhydride. 
Periodic  anhydride. 


71.  These  anhydrides  may  combine  with  water,  form- 
ing hydrates.  Formerly  it  was  supposed  that  these 
hydrates  contained  the  water  molecule,  H2O  ;  but  now 
it  is  generally  thought  that  they  bear  only  a  typical 
relation  to  water,  containing,  perhaps,  its  radical  hy- 
droxyl  ;  thus,  BaO  -f  II9O  =  Ba(OIT)2  ;  SO3  -j-  II2O  = 
S02(OH)2. 

In    accordance   with    this    view,   a  basic    hydrate  is  a 
compound    of  hydrogen   and  a  positive  atom  or  radical 


BASIC 

ANHYDRIDES. 

Na2O 

Sodium  oxide. 

S02 

Ag20 

Silver  oxide. 

SO., 

BaO 

Barium  oxide. 

C120 

CaO 

Calcium  oxide. 

C120, 

FeO 

Ferrous  oxide. 

N203 

Fe203 

Ferric  oxide. 

N205 

Hg20 

Mercurous  oxide. 

I2Or 

HgO 

Mercuric  oxide. 

I207 

TRUE  ACID   COMPOUNDS.  65 

united  by  oxygen.     These  hydrates  are   formed    on    the 
type  of  one  or  more  molecules  of  water. 


Type,  H2O. 


Type,  2H2O. 


K'  )  Ca"  ) 

jj,  ?•  O"  Potassium  hydrate.  ^,     [•  O"2   Calcium  hydrate. 

Or  we  may  consider  these  bodies  as  compounded  with 
hydroxyl;  thus,  K-OH;  Ca"(OH)'2,  as  if  derived  from 
water,  H-OH,  taken  as  often  as  is  necessary. 

72.  All  true  acids  are  compounds  of  hydrogen  with  a 
negative  atom  or  radical.  In  the  binary  acids,  like 
HC1,  HI,  this  union  is  direct.  These  acids  all  receive 
the  termination  ic,  as  HC1,  hydrochloric  acid.  In  the 
ternary  acids  the  union  is  effected  by  a  linking  atom 
of  oxygen. 

Some  acids  are  formed  on  the  type  of  one  molecule 
of  water  ;  as  : 


Nitric  acid,  H2O,  N2O5  or  HNO3  or     j£/2>O"  or  (HO)/NO/2. 

NO' 

Nitrous  acid,  H2O,  N2O3  or  HNO2  or    Jj,  >O"  or  (HO)/NO/. 

Others  are  on  the  type  of  two  molecules;  as,  (H2O)2  : 

Q(~V/ 

Sulphuric  acid,  H2O,  SO3  or  H2SO4  or   jj/  2>Ox/2  or  (HO)/2SO/^2. 

SO7' 

Sulphurous  acid,  H2O,SO2  or  H2SO3  or  g,    >Ox/2  or  (HO)/2SO//. 

A  few  are  on  the  type  of  three  molecules;  as,  (H2O)3  : 

Phosphoric  acid, 

pr>/// 
3H20,  P205  or  H3P04  or    j£     >O//3  or    (HO)/3PO///. 

3 

We  may  also  suppose  these  acids  to  be  formed  by  the 
union  of  hydroxyl  with  a  negative  radical,  as  in  the 
last  formula  given  in  each  of  the  above. 

Chem.—  5. 


66  CHEMISTRY. 

73.  These  acids  are  all  named  from  the  negative  rad- 
ical. If  only  two  acids  of  an  element  are  known,  the 
stronger  equivalence  is  indicated  by  the  suffix  ic,  and 
the  weaker  by  ous.  If  four  acids  exist,  the  prefix  per 
is  placed  before  the  higher  ic  acid,  to  indicate  the 
highest  combination,  and  the  prefix  hypo  before  the 
lower  ous  acid,  to  indicate  the  lowest.  Generally  these 
suffice :  the  other  acids,  if  any,  are  indicated  by  arbi- 
trary names. 

We  have  the  following  acids  of  chlorine  and  of  sulphur: 


HC1  Hydrochloric  acid. 

HC1O  Hypochlorous  acid. 

HC1O2  Chlorous  acid. 

HC1O3  Chloric  acid. 

HC1O4  Perchloric  acid. 


H2S        Hydrosulphurjc  acid. 
H2SO2   Hyposulphurous  acid. 
H2SO3  Sulphurous  acid. 
H2SOt  Sulphuric  acid. 
(Seep.  115). 


74.  A  salt  is  formed  by  the   substitution    of  a   metal 
for  the  hydrogen   in   an   acid.     Binary  compounds   like 
KI,  KC1,  NaCl  are  called  haloid  salts,  from  their  resem- 
blance to  the  last  named,  which  is  common  salt.     Their 
names  all  end  in  ide,  as  before  described. 

The  salts  which  contain  oxygen  are  ternary  com- 
pounds, and  are  called  oxy-salts.  These  derive  their 
names  from  the  acids  from  which  they  are  formed,  only 
changing  ic  to  ate,  and  ous  to  ite,  and  prefixing  the 
name  of  the  basic  element  or  radical.  Thus : 

KC1O  Potassium  hypochlorite,  or  hypochlorite  of  potassium. 

KC1O2  Potassium  chlorite,  or  chlorite  of  potassium. 

KC1O3  Potassium  chlorate,          or  chlorate  of  potassium. 

KC1O4  Potassium  perchlorate,     or  perchlorate  of  potassium. 

75.  Acids   are  said  to  be  monobasic,  bibasic,  tribasic, 
etc.,  according   to   the    number  of  hydrogen  atoms  they 
contain  that  may  be  replaced  by  a  positive  atom.     Thus, 
sulphuric  acid  is  bibasic,  because  it  has  two  replaceable* 
atoms  of  hydrogen.     If  one  is  replaced  by  a  monad,  an 


DOUBLE  SALTS.  67 

acid  salt  is  formed  ;  if  both  are  replaced  either  by  two 
monads  or  by  one  dyad,  a  normal  salt  is  formed.  For 
example  : 

KHSO4  is  the  acid  potassium  sulphate  (or  bisulphate). 

K2SO4  is  the  normal  potassium  sulphate. 

Pbx/SO4  is  the  normal  lead  sulphate. 

A12///F(SO4)3  is  the  normal  aluminium  sulphate. 

76.  Double    salts    are    those    in    which    the    hydrogen 
atom  is  replaced  by  atoms  of  two  different  metals. 

The  alums  are  familiar  examples.     Thus,  common  alum  has  the 
following  composition: 


A12O3,  3SO3  +  K,O,  SO3;    or  A12K2S4O16;    or  A1K,  (SO4)2. 

The  haloid  salts  also  form  double  salts*  which  are  ternary. 
The  double  chloride  of  potassium  and  platinum  has  the  formula: 

2KC1,  PtCl4,    or    K2PtCl6,    or   (KC1)2,  Cl//2(PtCl2). 

77.  Sulphur  acts  like  oxygen  as  a  linking  atom,  and 
there  exists  a  series  of  sulphur  compounds  analogous  to 
those  already  given  of  oxygen.  Thus  : 


K2S  is  a  basic  sulpho-anhydride. 

SnS2  is  an  acid  sulpho-anhydride. 

H2S  is  a  sulpho-acid. 

HS  is  its  radical. 

KHS  is  a  sulpho-base. 

H2SnS3  is  a  sulpho-acid. 

K2S,  SnS2,  or  K2SnS3,  is  a  sulpho-salt. 


OXYGEN    ANALOGUES. 


K00 


SnO 


HO 

KHO 

H2SnO3 


There  are  other  series  of  less  importance;  we  mention  only  that 
derived  from  hydrofluosilic  acid,  2HF,  Si,  F4,  in  which  the  hydrogen 
may  be  replaced  by  metals;  as,  2KF,  SiF4  or  K2  SiF6. 

78.  When  salts  are  dissolved  in  water,  and  the  solu- 
tion evaporated,  bodies  are  produced  which  have  regular 

"Such  double  salts  of  saturated  bodies  are  called  "molecular  compounds." 
The  linking  chlorine  appears  to  act  diatomic. 


68  CHEMISTRY. 

or  crystalline  forms.  These  crystals  are  frequently  found 
to  contain  a  molecule  of  the  salt  and  from  1  to  24  mole- 
cules of  water.  In  such  crystalline  molecules  the  water 
is  supposed  to  exist  as  such,  and  is  called  the  water  of 
crystallization.  The  water  is  an  essential  part  of  the 
crystalline  molecule,  but  not  of  the  chemical  molecule. 

This  is  evidenced  by  the  fact  that  the  same  saline  molecule  may 
combine  with  different  proportions  of  water  to  form  different  crys- 
talline forms.  Thus  sodium  carbonate  crystallizes  from  a  boiling 
solution  as  Na2CO3  -f-  H2O,  in  rectangular  tables ;  at  ordinary 
temperatures,  as,  Na2CO3  -f-  10H2O,  in  rhombic  prisms.  In  dry 
air  these  rhombic  prisms  lose  their  water  of  crystallization  and 
crumble  to  a  white  powder.  This  is  called  efflorescence.  Some 
crystals  require  a  higher  temperature  to  expel  their  water  of  crys- 
tallization. Blue  cupric  sulphate  is  CuSO4  -)-  5H2O.  It  loses  4 
molecules  of  water  when  dried  at  100°  C.,  and  does  not  give  up 
the  remaining  molecule  unlil  it  is  heated  to  200°  C.  It  then  forms 
a  white  powder,  CuSO4,  and  is  said  to  be  anhydrous.  The  last 
molecule  of  water  is  sometimes  called  the  water  of  constitution,  be- 
'  cause  it  seems  to  be  more  strongly  connected  with  the  saline 
molecule  than  the  others;  and  this  is  indicated  by  separating  it 
from  them  in  formulae;  thus,  H2O,  CuSO4  -f  4H2O. 

79.  The  notation  of  compounds  is  their  representation 
by  means  of  symbols  and  signs.  From  what  has  already 
been  said,  it  is  evident  that  this  will  vary  with  the  ideas 
which  are  intended  to  be  conveyed.  As  a  general  rule, 
the  positive  atoms  and  radicals  are  written  first.  A 
numeral  placed  below  a  symbol  multiplies  it  alone.  A 
numeral  placed  in  any  other  position  multiplies  every 
atom  by  itself  until  some  sign  of  separation,  as  a  bracket, 
parenthesis,  or  comma,  is  reached. 

In  mineral  chemistry,  the  dualistic  formula?  are  of  ad- 
vantage when  we  wish  to  express  that  the  same  anhy- 
dride is  common  to  several  compounds;  as,  K2O,  CrO3, 
and  K2O,  2CrO3  instead  of  K2CrO4  and  K2Cr2O7.  In 
organic  chemistry,  the  formula)  are  generally  structural. 
We  contrast  these  systems  by  the  following  equations. 


FORMULAE. 


69 


The  reactions  between  lead  nitrate  and  sulphuric  acid: 
EMPIRICAL.       PbN2O6  +  H2SO4  =  PbSO4  -f  H2N2O6. 
DUALISTIC.        PbO,  N205+H20,  SO3  =  PbO,  SO3-f  H2O,  N2O5. 
T™AL.  (NO,).  }  02+  SH 

STRUCTURAL. 


HO>S°2=Pb<0>S°2 


NOTE.— The  student  will  find  it  of  great  advantage  to  be  enabled  to  use 
readily  all  systems  of  formulae.  In  this  book,  although  preference  is  given 
to  structural  formulae,  the  dualistic  system  is  still  retained. 

In  many  of  the  older  text-books  on  chemistry,  different  atomic  weights 
were  assigned  to  the  elements,  giving  rise  to  a  different  set  of  formulae. 


Recapitulation. 

Atoms  differ  in — 

Weight  —  measured  relatively  by  the  hydrogen  unit. 
In  electrical  relations  —  positive  or  negative. 

monads  '  or  univalent;  as,  H'. 
perissads,  j  triads  /x/  or  trivalent;  as,  B//x. 

odd       1  pentads  v  or  quinquivalent;  as,  Nr 
In  combining  heptads  ™  or  septivalent;  as, 

power 

f  dyads  "  or  divalent;  as,  O". 

-<  tetrads  IV   or  quadrivalent;   as,  C/r. 

(^  hexads  VI  or  sexivalent;  as,  Sr/. 


even 


Molecules  are 


(composed  of  like  atoms  —  elementary;    as,  H2. 


1  composed  of  unlike  atoms  —  compound;    as,  HC1. 

Radicals  are  residues  of  molecules,  and  act  as  atoms. 

Thev  are  I  e^her  an  elementary  atom,  as  H, 

(  or  an  nnsaturated  molecule,  as  HO. 


70 


CHEMISTRY. 


Saturated 

compounds 

are  classified 


f  basic  anhydrides;    as,  K2O. 
binary  oxides  1  acid  anhydrides;    as,  SO3. 

(_  neutral  bodies;    as,  MnO2,  H2O. 

basic  hydrates;   as,  KHO. 

(  binary  or  haloid  acids;    as,  HC1. 
s  '     '     '       (ternary  acids;    as,  H2SO4. 

f  binary  or  haloid  salts;   as,  KC1. 
salts  •<  ternary  salts;    as,  K2S04. 

(double  salts;   as,  KA1(SO4)2. 


The  actual  proportion  of  atoms  in  a  compound  is  always  denoted 
by  numerals;  as,  HC1,  H2O,  Hg2Cl2,  HgCl2,  which  take  the 
names,  prot,  1;  bi,  2;  ter,  3;  telra,  4;  penta,  o;  sesqui,  2:3. 

The  relative  proportion  of  atoms  in  the  compounds  of  a  given  ele- 
ment, as  R,  is  denoted  by  prefixes  and  suffixes. 

The  highest  equivalence  of  four  compounds  by    per — R — ic. 

"          "  "  "   two          " "  "  R — ic. 

The  lowest  "  "  two  "  "  R — ous. 

"  "  "  "    four  "  "   hypo — R — ous. 

The  termination  ide  is  applied  only  to  binaries;    as,  KC1. 

The  terminations  of  ternary  salts  are: 

ite,  when  the  acid  ends  in  ous;   as,  K2SO3. 
ate,       "       "        "        "       "    ic;   as,  K2SO4. 

The  termination  of  compound  radicals  is  yl;   as,  HO. 

NOTE.— Since  this  book  was  electrotyped,  the  London  Chemical  Society  has 
advised  some  changes  in  Notation  and  Nomenclature,— as  hydroxide  for  hydrate 
in  those  compounds  which  are  supposed  to  contain  hydroxyl,  OH.  Most  of 
these  changes  have  been  made,  but  the  student  is  requested  to  make  the  one 
mentioned  for  himself,  or  to  regard  the  two  words  as  synonymous. 


CHAPTEE    IV. 


WATER    AND    ITS    ELEMENTS. 


ELEMENT. 

SYMBOL. 

WT.  OF  ONE 
LITRE  IN 
GRAMMES. 

SPECIFIC 

AIR  =  1. 

GRAVITY. 
H  =  1. 

jj 

DISCOVERER. 

Hydrogen    .  . 
Oxygen  .... 

H 
0 

.0896 

1.4336 

.0692 
1.1056 

1. 
16. 

1 

16 

Cavendish,  1766. 
Priestley,  1774. 

,„_         (Steam 

Water  ^  , 
(Liquid 

H20 
H20 

.8064 
1000. 

.622 
773. 

9. 
11160. 

Investigated  by 
Lavoisier,  1781. 

80.  We  have  already  learned  that  water  is  composed 
of  hydrogen    and    oxygen,    in    the    proportions    of  two 
volumes  of  hydrogen  to  one  of  oxygen,  or,   by  weight, 
of  2  parts  "of  hydrogen  to  16  of  oxygen. 

HYDROGEN. 

81.  Hydrogen  is  an  essential  constituent  of  water,  of 
acids,  and  of  most  organic  compounds. 

It  may  be  obtained  from  any  of  these  bodies.  From 
water,  (1)  by  the  electrical  current  (Art.  47) ;  (2)  by 
passing  steam  over  iron  filings  heated  to  redness  (Exp. 
29) ;  (3)  from  cold  water  by  the  action  of  sodium  (Exp. 
4)  ;  (4)  by  placing  bright  zinc  strips  in  water.  In  this 
case  the  zinc  decomposes  the  water,  forming  zinc  oxide 
and  setting  the  hydrogen  free:  Zn  -j-  H2O  =  ZnO  +H2. 
The  action  soon  ceases,  because  the  zinc  becomes  coated 
with  an  insoluble  film  of  the  oxide,  which  prevents 
further  oxidation. 

(5)  If,  however,  the  water  is  mixed  with  one-fifth  of 
its  weight  of  sulphuric  acid,  the  action  is  continuous, 

(71) 


72  CHEMISTRY. 

because  the  acid  unites  with  the  oxide  as  fast  as  it 
is  formed  to  produce  zinc  sulphate,  ZnO,  SO3,  which 
readily  dissolves  in  the  excess  of  water,  and  thereby 
the  surface  of  the  zinc  is  kept  bright  and  clean.  We 
may  suppose  that  the  two  reactions  occur  simultane- 
ously, and  that  the  molecule  of  water  decomposed  is 
that  previously  in  combination  with  the  acid,  and  may 
represent  the  process  by  a  single  equation  : 

Zn  +  H20,  S08  =  ZnO,  SO8  +  fl2. 

If  too  little  water  is  present,  a  sulphate  is  produced 
which  is  with  difficulty  soluble,  and  the  action  is  less 
energetic. 

82.  A  convenient  apparatus  is  shown  in   Fig.  20:    a  represents 

a  flask  containing  a  handful  of 
granulated  zinc;*  b  is  a  funnel 
reaching  almost  to  the  bottom  of 
the  flask,  through  which  the  acidu- 
lated water  may  be  poured  as  re- 
quired; and  c  is  a  tube  just  passing 
through  the  cork  for  the  escape  of 
the  gas.  The  end  of  the  tube,  d, 
may  be  placed  under  a  receiver,  as 
the  cylinder  e.  The  cylinder  is 
pIG  20  first  to  be  filled  with  water  and 

inverted    in    a   suitable  cistern  also 

containing  water.  As  the  hydrogen,  at  first,  is  mixed  with  the 
air  of  the  flask,  none  of  the  escaping  gas  should  be  employed  in 
experiments  until  the  air  has  been  thoroughly  expelled  from  the 
apparatus.  The  moment  when  this  result  is  reached  may  be  ascer- 
tained by  filling  test  tubes  with  the  escaping  gas  in  the  water  cis- 
tern, and,  after  lifting  them  carefully  from  the  water  without 
changing  their  vertical  position,  applying  a  lighted  match  to  the 
mouth  of  the  tube.  If  the  hydrogen  is  free  from  air,  it  will  burn 
quietly;  but  if  much  air  is  present,  the  mixture  will  be  ignited 
with  a  sharp  explosion. 

*  Zinc  is  granulated  by  melting  zinc  scraps  in  an  iron  ladle,  and  slowly  pour- 
ing the  molten  metal  from  a  height  into  a  pail  tilled  with  cold  water. 


PHYSICAL  PROPERTIES  OF  HYDROGEN. 


73 


NOTE.— When  explosions  are  anticipated  in  the  process  of  experiment,  the 
quantities  operated  on  should  be  small ;  and,  in  the  case  of  gases,  the  vessels  in 
which  they  are  contained  should  be  of  thick  glass.  Even  in  this  case,  it  is 
prudent  to  wrap  glass  vessels  in  a  thick  towel  before  applying  the  match. 

The  hydrogen  obtained  from  zinc  is  liable  to  certain  impurities, 
which  may  be  sufficiently  removed  by  passing  the  gas  through 
three  bottles  containing,  respectively,  (1)  a  dilute  solution  of  sodium 
hydrate,  (2)  a  dilute  solution  of  silver  nitrate,  and  (3)  small  lumps 
of  charcoal.  A  fourth  wash  bottle,  containing  strong  sulphuric 
acid,  may  also  be  used  to  dry  the  gas. 

The  dry  gas  may  be  collected  over  quicksilver,  or  used  in  ex- 
periments which  require  only  a  stream  of  the  gas.  The  fourth 
bottle  is  unnecessary  when  the  hydrogen  is  collected  over  water. 


FIG.  21. 

83.  The  Physical  properties  of  hydrogen  make  it  a 
convenient  standard  for  the  density  of  aeriform  bodies, 
Hydrogen  is  14.43  times  lighter  than  air.  It  is  a  color- 
less, odorless,  tasteless  gas  which  has  been  liquefied  under 
a  pressure  of  280  atmospheres.  When  this  liquid  was 
allowed  to  expand  suddenly,  the  cold  produced  was 
sufficient  to  condense  a  portion  to  a  fine  spray  contain- 
ing solid  particles  which  rattled  like  shot. 

Exp.  62. — Prepare  a  solution  of  soap,  and,  by  means  of  a  to- 
bacco pipe  connected  with  the  evolution  tube,  inflate  soap  bubbles 
with  hydrogen.  When  detached  from  the  pipe  they  rise  rapidly, 
showing  that  hydrogen  is  lighter  than  air.  Small  bags  made  of 
caoutchouc  and  filled  with  the  gas  will  rise  like  a  balloon. 


74 


CHEMISTRY. 


Owing   to    its    lightness,   jars    may  be    lilled  with  the 
gas  by  displacement. 

Exp.  63. — This  may  be  done  by  fitting  a  ver- 
tical tube  to  a  flask  from  which  the  gas  is  escaping 
rapidly,  and  by  holding  over  this  a  dry  cylinder 
(Fig.  22).  After  a  few  minutes,  the  hydrogen  will 
be  found  to  have  so  completely  displaced  the  air 
of  the  cylinder  that  no  explosion  will  ensue  when 
a  lighted  taper  is  applied  to  the  mouth  of  the 
cylinder. 

Exp.  64, — So,  also,  hydrogen  may  be  poured 
from  one  cylinder  to  another  (Fig.  23),  if  we  only 
remember  that  in  pouring  hydrogen  the  gas  will  flow  up,  and  not 
down  as  is  the  case  in  pouring  water.  Unless  the  receiving  cyl- 
inder is  much  smaller  than 
the  other,  all  its  air  will  not 
be  displaced,  and  now  an 
explosion  may  be  expected  ^  , 

when  a  lighted  taper  is  ap- 
plied at  its  mouth. 


FIG.  22. 


84.  Hydrogen  is  taken 
as  the  unit  of  atomic 
weights.  Its  rate  of 
diffusion  is  the  highest  FIG.  23. 

known.     This  is  due  to 

its  high  rate  of  molecular  motion.     (See  note  to  p.  52). 
It  diffuses  3.8  times  faster  than  air. 

Exp.  65. — Close  the  mouth  of  a  glass  funnel  having  a  long 
delivery  tube  by  a  septum  of  plaster  of  Paris.  This  may  be  done 
by  making  a  moderately  thick  paste  of  the  plaster  with  water  on 
a  plate,  inverting  the  mouth  of  the  funnel  therein,  then  suffering 
the  plaster  to  harden  and  to  dry  thoroughly.  Detach  the  funnel 
from  the  plate,  and  place  the  open  tube  in  colored  water,  inverting 
over  the  closed  mouth  a  jar  filled  with  hydrogen.  The  hydrogen 
diffuses  into  the  funnel  faster  than  the  air  diffuses  out,  and  soon 
bubbles  of  gas  escape  through  the  water.  Now  remove  the  jar, 
and  the  hydrogen  will  escape  in  the  contrary  direction,  leaving 
a  partial  vacuum  in  the  funnel,  which  becomes  manifest  by  the 
rise  of  water  in  the  tube. 


CHEMICAL  PROPERTIES  OF  HYDROGEN.          75 

A  beautiful  modification  of  this  is  shown  in  Fig.  24.  A  large  diffu- 
sion tube  is  attached  to  a  two-necked 
flask,  which  has  a  tube  extending 
through  the  second  neck  below  the 
surface  of  some  wrater  contained  in 
the  flask.  If  the  septum  is  dry 
and  the  fittings  are  air-tight,  a 
fountain  of  water  will  be  formed 
of  considerable  height. 

Exp.  66. — A  curious  experiment 
which  shows  that  sound  is  much 
enfeebled  in  hydrogen  may  be  per- 
formed by  filling  the  lungs  of  the 
experimenter  with  pure  hydrogen 
and  his  then  attempting  to  speak. 
The  voice  will  be  weak  and  piping. 

85.  Chemical  properties.  The 

following  experiments  illus- 
trate some  of  the  chemical 
properties  of  hydrogen. 

Exp.  67. — Fill  a  cylinder  with 

dry   hydrogen,    and   introduce   into 

this  a  lighted  wax  taper.  (Fig.  25.)  The  gas  will  be  enkindled 
at  the  mouth  of  the  cylinder.  If  the  taper  is 
pushed  up  into  the  cylinder,  its  flame  will  be  ex- 
tinguished. On  withdrawing  the  taper,  it  may  be 
again  ignited  by  the  burning  gas,  then  again  ex- 
tinguished by  passing  it  upward  into  the  gas,  and 
then  rekindled  for  several  times  in  succession. 

This   shows  that   hydrogen    burns  when 
in   contact  with   the   air,   hut  that  it  does 
FIG.  25.          not  support  ordinary  combustion. 

Exp.  68. — Attach  to  the  drying  bottle  a  vertical  tube  drawn 
out  so  as  to  yield  a  small  jet,  as  in  Fig.  26.  If  the  jet  of  gas  be 
ignited,  it  will  burn  with  an  almost  non-luminous  flame.  Hold 
over  this  flame  an  evaporating  dish  containing  ice.  The  outside 
of  the  dish  will  become  covered  with  moisture,  and  in  a  short 
time  will  yield  drops  of  water. 


CHEMISTRY. 


This  experiment  may  be  modified  by  burning  the  jet  within  a 
wide  glass  tube.  The  upper  part  of  the  tube  will  be  covered  with 
condensed  water.  At  the  same  time,  a  mu- 
sical note  will  be  produced,  which  will  vary 
in  pitch  as  the  tube  is  raised  or  lowered. 
The  sound  is  due  to  a  series  of  small  explo- 
sions in  rapid  succession,  which  produce  reg- 
ular vibrations  in  the  air  column  of  the  tube. 

86.  The  product  of  the  combustion 

of  hydrogen  in  air  is  water.  From 
this  fact  the  gas  derives  its  name. 
The  reason  why  the  flame  is  so  feebly 
luminous  is  that  neither  the  particles 
of  the  gas  nor  of  the  steam  which 
is  formed  become  incandescent.  The 
FlG  gg  flame  is  nevertheless  very  hot. 

Exp.  69. — Hold  in  the  flame  a  solid  body,  as  a  thin  platinum 
wire  or  a  bit  of  chalk  sharpened  to  a  point.  The  solid  particles 
will  soon  become  white  hot,  and  the  flame  increase  perceptibly  in 
illuminating  power. 

The  heat  evolved  by  the  combustion  of  one  gramme 
of  hydrogen  is  34462  thermal  units.  The  temperature 
attained,  under  favorable  conditions,  is  very  nearly 
2800°  C. 

87.  Hydrogen  is  a  powerful  reducing  agent. 

Exp.  70. — If  the  dry  gas  be  passed  through  a  tube  containing 
cupric  oxide  kept  at  a  low  red  heat,  metallic  copper  will  be  pro- 
duced. (Fig.  27.)  The  oxygen  previously  combined  with  the  copper 
unites  with  the  hydrogen  to  form  steam.  (See  Exp.  30). 

88.  Hydrogen  acts  energetically  in  what  is  known  as 
the   nascent  state;   that  is,  at  the  moment  that  it  is  set 
free,  and  before  it  becomes  perceptible  to  the  eye. 

Exp.  71. — Place  in  a  beaker  a  strip  of  zinc;  place  upon  this 
silver  chloride  (Exp.  57),  and  cover  both  with  very  dilute  hydro- 


USES  OF  HYDROGEN.  77 

chloric  acid.  In  a  few  hours  the  silver  will  be  reduced  to  the 
metallic  state  through  the  union  of  its  chlorine  with  the  hydrogen 
set  free  by  the  action  of  the  acid  upon  the  zinc. 


FIG.  27. 

89.  Hydrogen   is   absorbed,   or   "occluded,"   by   many 
metals  in  large  quantities.     Palladium  absorbs  935  times 
its  volume  of  hydrogen,  and  forms  a  substance  which  is 
apparently  an   alloy.     For  this  reason  Graham  inferred 
that  hydrogen  is  a  metal. 

TESTS. — Hydrogen  may  be  recognized  by  its  physical  properties 
and  by  its  combustibility,  but  more  certainly  by  the  fact  that  two 
volumes  of  the  gas  mixed  with  one  volume  of  oxygen,  and  ex- 
ploded, form  water. 

90.  Physiological  properties.     Although  the  lungs  may 
be    filled   once   with   pure   hydrogen    without   danger,   it 
does   not   support   respiration.     Small    animals    confined 
in  it  speedily  die. 

91.  The  only  uses  which  have  been  made  of  hydrogen 
are :    (1)   as   a  source   of  heat  in   melting  platinum  and 
other  refractory  metals ;    (2)  to  render  the  calcium  em- 
ployed   in    the    Drummond    light    highly   incandescent; 
and  (3)  as  a  material  for  filling  balloons. 


78 


CHEMISTRY. 


OXYGEN. 

92,  Oxygen  is  found  uncombined  in  the  air,  and  is  a 
constituent  of  water,  of  most  minerals,  and  of  many 
organic  bodies,  like  sugar,  starch,  and  alcohol. 

It  may  be  obtained,  (1)  by  the  electrolysis  of  water 
(Art.  47),  and  (2)  by  heating  many  of  the  higher 
oxides,  as,  HgO,  MnO2,  Pb8O4,  I2O6.  (Sec  §§  413,  507). 

It  is  most  conveniently  prepared  by  heating  potassium  chlorate, 
KC1O3.  One  gramme  of  this  salt  yields  273.8  cubic  centimetres 
of  oxygen,  and  a  residue  of  6  decigrammes  of  potassium  chloride, 
KC1O3  =  KC1  -f  3"t).  At  a  gentle  heat,  one-third  of  the  oxygen 
is  given  off— 2KC1O3  =  KC1O4  -f-  KC1  -f  O"a— and  potassium  per- 

chlorate  is  formed. 
This  body  at  a 
higher  temperature 
also  decomposes  and 
yields  the  remaining 
oxygen  — KC1O4  = 
KC1  -f  "6"4— but  the 
gas  is  evolved  so 
rapidly  that  consid- 
erable dexterity  is 
required  in  manipu- 
lation. Where  large 
quantities  are  re- 
quired, it  is  better 
to  use  a  mixture  of 

FIG.  28.  equal  parts  of  man- 

ganese  dioxide   and 

potassium  chlorate.  The  reaction  is  the  same  as  before.  The  man- 
ganese dioxide  is  not  decomposed,  but  by  its  presence  regulates 
the  action,  and  the  mixture  requires  less  heat  than  the  chlorate 
alone.* 

The  process  may  be  conducted  in  a  stout  glass  flask,  as  shown 
in  Fig.  28.  A  retort  of  iron  or  copper  is  very  convenient. 

*  It  is  advisable  to  heat  the  manganese  dioxide  to  redness,  and  then  cool  it 
before  using,  because,  if  it  contains  carbon,  explosive  compounds  are  sometimes 
formed. 


OXYGEN. 


79 


93.  Physical  properties.     Oxygen  may  be  collected  over 
water,  as  100  volumes  of  water,  at  15°  C.,  absorb  but  3  of 
this  gas.     It  is  colorless,  odorless,  and  tasteless,  and  has  re- 
cently been  liquefied  under  a  pressure  of  320  atmospheres. 

94.  Chemical    properties.     Oxygen    forms    compounds 
with  all  of  the  elements  except  fluorine.     We  have  seen 
that  ordinary  combustion  is  due  to  the  union    of  bodies 
with  oxygen.     Any  substance    which    will    burn    in    air 
will  burn    far    more  brilliantly  in  pure  oxygen ;    others, 
that  are  generally  considered   incombustible,  burn  with 
violence  in  oxygen. 

Exp.  72. — Having  lighted  a  small  taper,  blow  it  out  so  as  to 
leave  a  small  spark  on  the  wick.  Plunge  this  into  a  jar  of  oxygen. 
It  will  be  immediately  rekindled.  It  may  then  be  again  blown 
out  and  rekindled  so  long  as  the  gas  remains. 

Exp.  73.— Place  a  little  sulphur  in  a  de- 
flagrating spoon;  kindle  this  in  the  flame  of 
a  lamp  and  plunge  it  into  a  jar  of  oxygen. 
The  sulphur  will  burn  with  a  lilac  flame. 

Exp.  74. — Repeat  the  last  experiment 
with  a  small  piece  of  dry  phosphorus,  *  and 
ignite  it  by  a  hot  wire.  On  plunging  it  into 
the  oxygen,  it  will  burn  with  dazzling  brill-  FIG,  29. 

iancy. 

Exp.  75. — Coil  an  iron  wire  into  the  form 
of  a  spiral  by  winding  it  around  a  pencil. 
Pass  one  end  through  a  cork  which  fits  the 
mouth  of  the  jars  used,  and  tip  the  other 
with  melted  sulphur  or  tinder.  Set  fire  to 
the  tinder  and  plunge  the  wire  into  a  jar 
of  the  gas.  The  iron  will  take  fire  and  burn, 
throwing  out  bright  sparks. 

FlG  3Q  Steel  gives  more  brilliant  effects.    A  broken 

watch   spring,  straightened  by  heating   so   as 
to  destroy  its  temper,  may  be  used  instead  of  the  iron  wire. 

These  experiments  may  be  extended  by  using,  (1)  on  the  spoon, 
a  pellet  of  napthalene  or  of  potassium;  (2)  attached  to  a  wire,  a 

*  Phosphorus  should  neither  be  handled  nor  cut  except  under  water. 


80 


CHEMISTRY. 


bit    of  charcoal,    or    strips   of  zinc,    thin    copper,   etc.     Magnesium 
wire  burns  brilliantly  even  in  ordinary  air. 

The  experiments  may  be  modified  by  using,  instead  of  jars  filled 
with  oxygen,  a  stream  of  the  gas.  If  the  student  does  not  possess 
a  suitable  gas  holder,  he  may  use  large  ox  bladders  softened  in 
water  and  then  well  rubbed  with  glycerine.  These  bladders  are  to 
be  tightly  fitted  with  a  glass  tube,  the  air  pressed  out,  and  then 

inflated  with  oxygen.  A  temporary 
stopper  for  the  tube  may  be  made  by 
slipping  over  the  end  a  bit  of  rubber 
tubing,  and  plugging  up  the  open  end 
of  the  rubber  tube  with  a  glass  rod. 

Exp.  76. — Place  a  pellet  of  phos- 
phorus in  a  conical  wine-glass,  and 
pour  enough  hot  water  over  the  phos- 
phorus to  melt  it.  Now  force  a  stream 
of  oxygen  on  the  melted  phosphorus. 
It  will  burn  under  the  water. 

FIG.  31. 

Exp.  77.— Arrange  a  combustion 

tube  as  shown  in  Fig.  32.     Place  in  one  end  of  the  tube  a  bit  of 
sulphur,    or   of  coal,    or   of  potassium,  etc.,  and   connect  with  the 
other   end    tubes   plunged 
in    empty  jars   to   collect 
such   products  as  may  be    » 
volatile.      Now     force     a 
stream   of  the  gas,    dried 
by  passing  it  through  sul- 
phuric  acid,   through    the 
tube,  and  ignite  the  bodies 
placed    in    it    by   heating 
them  with  the  flame  of  a 
lamp.  They  will  burn  bril- 
liantly, as   in   the   former 
cases.  FIG.  32. 


95.  The  products  of  the  combustion  .should  be  tested. 
If  a  little  water  be  poured  into  the  jars  and  shaken  up, 
the  charcoal  jar  will  be  found  to  contain  carbonic  acid ; 
the  sulphur,  sulphurous  acid ;  the  phosphorus,  phos- 
phoric acid.  These  solutions  will  each  redden  blue 


TESTS  FOR   OXYGEN.  81 

litmus.      The   potassium  residue,  moistened  with   water, 
will  change  red  litmus  to  blue.     It  is  alkaline. 

96.  Tests  for  free  oxygen.  When  oxygen  is  not  much 
diluted  with  other  gases,  it  may  be  tested  by  plunging 
into  the  jar  containing  it  a  splinter  of  pine  tipped  with 
a  glowing  coal.  If  the  coal  bursts  into  a  flame,  the  gas 
is  either  oxygen  or  nitrous  oxide. 

Oxygen  is  not  absorbed  by  potassium  hydrate,  but  if 
potassium  hydrate  is  mixed  with  pyrogallic  acid,  the 
alkaline  pyrogallate  which  is  formed  rapidly  absorbs 
oxygen  and  becomes  black.  This  is  not  only  a  valuable 
test  for  free  oxygen,  but  it  may  be  used  to  absorb 
oxygen  from  gaseous  mixtures. 

Exp.  78.— Take  a  long  tube  closed  at  one  end,  and  pour  into 
it  a  spoonful  of  a  solution  of  potassium  hydrate.  Now  drop  into 
the  tube  a  few  flakes  of  pyrogallic  acid.  Close  the  tube  with  the 
thumb,  and,  after  shaking,  invert  it  in  a  dish  of  water  The 
pyrogallate  will  be  blackened,  and,  on  removing  the  thumb,  the 
water  will  rise  in  the  tube,  because  the  oxygen  has  been  absorbed 
from  the  air  contained  within  it. 

97  Physiological  properties.  If  a  small  animal  be 
confined  in  a  jar  of  oxygen,  its  respiration  becomes 
increased ;  it  becomes  feverish  and  soon  dies,  because 
of  the  too  great  supply  of  oxygen.  Diluted  with  nitro- 
gen, it  is  essential  to  the  respiration  of  all  animals. 

Exp.  79. — Shake  up  a  little  fresh  venous  blood  in  a  jar  of  oxy- 
gen; it  will  quickly  become  changed  to  red,  or  arterial,  blood.  This 
is  the  change  which  goes  on  continually  in  our  lungs. 

98.  Uses  of  oxygen.  We  have  already  seen  that  oxygen 
is  an  active  agent  in  promoting  chemical  changes  in  the 
laboratory  of  the  chemist  and  in  the  greater  workshop 
of  Nature.  The  processes  of  respiration,  of  ordinary 
combustion,  of  fermentation,  and  of  decay  are  all  de- 
pendent upon  it. 

Chem.— 6. 


82  CHEMISTRY. 

99.  Since  these  various   processes    of  oxidation   con- 
sume oxygen,  it  may   be  supposed  that  the  time  might 
come  in  which  the  atmosphere  would  no  longer  contain 
it,    and,    therefore,   that    respiration    would    become    im- 
possible and  animal  life  cease.     Lehmann  has  calculated 
that   the    air    contains    enough    oxygen    to    last   800,000 
years ;  but  the  agencies  of  nature  so  balance  each  other 
that  the  proportions  of  the  atmosphere  remain  unchanged. 

The  principal  products  of  combustion  and  respiration 
are  carbonic  anhydride  and  water.  These  are  necessary 
to  the  growth  of  plants.  They  consume  them  to  form 
the  materials  which  we  use  for  food  and  fuel.  The 
green  parts  of  the  plants  evolve,  in  the  sunlight,  the 
oxygen  required  for  animal  life. 

Exp.  80. — Place  a  handful  of  fresh  green  leaves  in  a  bell  glass. 
Fill  tliis  completely  with  water,  and  invert  on  a  plate  also  con- 
taining water.  Now  expose  the  leaves  to  the  bright  sunlight  for 
several  hours.  Bubbles  of  gas  will  collect  in  the  upper  portion 
of  the  glass,  which  on  examination  will  prove  to  be  oxygen. 

100.  The   oxy-hydrogen  blowpipe   is  one  of  the  most 
efficient  artificial  sources  of  heat  and  light.     This  is  an 
apparatus  so  contrived   that   two   volumes   of  hydrogen 
are  burned  with   one   volume  of  oxygen.     It  is  exceed- 
ingly dangerous  to  ignite  large  quantities  of  these  gases 

previously  mixed ;  hence, 
a  double  jet  is  used,  as 
shown  in  Fig.  33. 

FlG  33  The  interior  jet,  O,  supplies 

a  stream   of  oxygen,  and  the 

outer  jet,  H,  a  stream  of  hydrogen.  The  hydrogen  is  first  turned 
on  and  enkindled;  the  oxygen  is  then  forced  through  the  hydrogen 
flame,  and  the  two  gases  burn  at  the  moment  of  mixing. 

If  both  gases  are  pure  and  dry,  the  flame  is  feebly 
luminous,  but  intensely  hot.  Strips  of  iron,  copper, 
zinc,  etc.,  burn  with  great  brilliancy  in  it.  Metals  like 


OZONE.  83 

antimony  and  arsenic  are  exposed  to  its  action  by  sup- 
porting them  on  bits  of  charcoal.  All  the  metals,  with- 
out exception,  are  melted  by  it.  By  directing  this  jet 
into  the  interior  of  a  small  furnace  lined  with  lime, 
Deville  has  succeeded  in  melting  100  kilogrammes  of 
platinum  at  a  single  charge. 

If  the  jet  be  directed  on  the  stem  of  a  clay  tobacco 
pipe,  it  fuses.  Lime  does  not  fuse  in  the  jet,  but  be- 
comes so  highly  incandescent  as  to  yield  a  very  pure 
white  light  of  dazzling  brilliancy.  This,  properly  mounted 
in  the  focus  of  a  concave  mirror,  has  been  used  for  sig- 
nalling, under  the  name  of  the  Drummond,  or  calcium, 
light.  It  has  been  seen  at  a  distance  of  more  than  100 
miles. 

Exp.  81. — Inflate  soap  bubbles  with  a  mixture  of  two  volumes 
of  hydrogen  and  one  of  oxygen.  After  they  have  risen  from  the 
jet,  apply  a  lighted  taper.  A  bubble  the  size  of  a  tumbler  will 
explode  with  a  loud  report. 

Such  mixtures  of  oxygen  or  of  air  with  hydrogen  or  illuminating 
gas,  or  with  the  vapors  of  coal  oils,  are  dangerously  explosive. 

101.  Ozone.  Whenever  an  electrical  machine  is  in 
operation,  a  pungent  odor  is  developed  in  the  air 
through  which  the  sparks  pass.  The  same  odor  is  per- 
ceived when  a  clean  stick  of  moistened  phosphorus  is 
allowed  to  remain  for  two  hours  in  a  large  flask  loosely 
stoppered.  In  both  cases  the  odor  is  due  to  a  change 
effected  in  the  oxygen  of  the  air,  by  which  it  becomes 
remarkably  energetic.  This  modification  of  oxygen  is 
called  ozone.  Ozone  may  also  be  prepared  by  shaking 
a  little  ether  in  a  jar  so  as  to  fill  it  with  vapor,  and 
then  plunging  a  heated  glass  rod  into  the  jar. 

No  method  has  been  devised  of  obtaining  ozone  pure. 
It  is  always  mixed  with  common  oxygen,  but  has  been 
obtained  by  induced  electricity  in  as  great  a  proportion 
as  15  per  cent.  Even  two  per  cent  will  suffice  to  ex- 
hibit its  wonderful  properties. 


84  CHEMISTRY. 

102.  Physical  properties.    Ozone  is  condensed  oxygen. 
It  is  re-converted  by  heat  into  ordinary  oxygen  with  a 
permanent   increase   of  volume.     Its   specific   gravity  is 
probably    1 J   times   that   of  oxygen :    hence,  a  molecule 
of  ozone    contains    three    atoms    of  oxygen,   while    the 
molecule  of  ordinary  oxygen  contains  two  atoms.  * 

103.  Chemical  properties.     Ozone  is  the  most  energetic 
oxidizer  known.     Even  in  the  dilute  state  it  is  capable 
of  bleaching  indigo,  oxidizing   silver   and    other  metals, 
and   displacing  hydrogen  from  its  compounds  with  sul- 
phur  and   iodine.     Caoutchouc   and   other   organic   sub- 
stances are  quickly  corroded  by  it. 

TESTS. — When  ozone  acts  upon  potassium  iodide,  potassium  oxide 
is  formed  and  iodine  is  liberated.!  Hence,  we  may  use  this  re- 
action in  two  ways  as  a  test  for  ozone. 

Exp.  82. — (1)  Moisten  red  litmus  paper  with  a  solution  of  po- 
tassium iodide;  when  the  potassium  oxide  is  formed  by  the  ozone, 
it  colors  the  paper  blue.  (2)  Moisten  unsized  paper  with  a  dilute 
solution  of  potassium  iodide,  containing  a  little  boiled  starch.  The 
iodine  set  free  by  the  ozone  colors  the  starch  blue.  If  much  ozone 
is  present,  the  iodine  changes  to  iodic  anhydride  I2O5,  and  the  paper 
is  again  bleached. 

104.  Ozone    is    frequently    found    in    the    atmosphere. 
This   ozone   is  probably  produced    by  the    processes    of 
oxidation  which    are    every-where   going  on   in   nature. 
The  slow  oxidation  of  turpentine  and  of  many  ethereal 
oils   is   attended   by  the   production  of  ozone,  especially 
if  these  bodies  are  exposed  to  the  sunlight. 

105.  Uses.     The  bleaching  power  of  the  air  is  due  to 
the    ozone   which    it   contains.     The    atmospheric   ozone 
destroys    the    malarious    exhalations    which    arise    from 
decaying   animal    and   vegetable   matters.     It  is  difficult 
to  over-rate  its  usefulness  as  a  disinfecting  agent. 

~   o 
A 

*  Oxygen,  O=O  ;   Ozone,  O—O.       f  2KH  O  =  K2O  +  21.    K2O  +  H2O  =2KHO. 


WATER.  85 

It  has  been  noticed  that  when  the  air  is  charged 
with  ozone,  epidemic  diseases,  like  cholera,  have  abated. 
Conversely,  air  highly  charged  with  ozone  is  irrespira- 
ble.  It  attacks  the  organs  of  respiration  and  produces 
coughing;  hence  it  is  supposed  to  assist  in  producing 
epidemics  of  catarrh  and  influenza. 

106.  Antozone.     Some  suppose  that  whenever  ozone  is 
formed,  another  modification  of  oxygen  is  also  produced. 
This  is  called  antozone.     Its  molecule   contains   but   one 
atom.     The  white  clouds  which  are  formed  when  ozone 
is  liberated  in  the  presence  of  water  are  supposed  to  be 
due   to   the   peculiar   property   which   antozone    has    of 
forming  clouds  or  mists  with  water.     The   existence   of 
antozone  is,  however,  still  questioned. 

107.  Oxygen  has  at  least  two  modifications,  ordinary 
oxygen  and  ozone.     Although  these  have  different  prop- 
erties, one  may  be  converted  into  the  other  without  loss 
of  weight.     Several    other   elements   occur   in    different 
states.     These   different   states   are  said  to  be  allotropic/ 
forms   of  the    element;    the    word    allotropy    signifying 
of  a  different  character. 

WATER  OR  HYDROGEN  OXIDE,  H2O. 

108.  Water  is  seldom  found  pure.     The  rain  that  falls 
in  open   fields   near  the   end   of  a   long  shower  is  very 
nearly   pure    water.      Although    the   great    part    of  the 
water   of  our   globe    occurs   in    its    free    state,  it   enters 
largely  into   mineral   combinations,   and   is,   besides,  es- 
sential to  vegetable  and  animal  structures. 

109.  We   have    shown    that   water   is    formed   by   the 
union    of   oxygen    with    hydrogen.      It    is    one    of   the 
products  formed  when  an  organic  substance    containing 
hydrogen  is  burned  in  air.     It   is   prepared   sufficiently 


86 


CHEMISTRY. 


pure   for   practical   purposes  by  the  distillation  of  ordi- 
nary water. 

Fig.  34  represents  an  apparatus  that  may  be  used  for  this  pur- 
pose. A  is  a  capacious  flask  in  which  rain  or  well  water  is  boiled: 
the  escaping  steam  is  cooled  by  passing  through  a  condenser,  B. 


FIG.  34. 


The  form  in  the  figure  is  known  as  Liebig's  condenser.  It  is  kept 
constantly  cool  by  a  stream  of  cold  water  entering  at  the  bottom 
and  flowing  out  at  the  top.  The  product  of  the  distillation,  which 
is  called  the  distillate,  is  collected  in  the  receiver,  C.  The  first 
portions  of  the  distillate  are  thrown  away,  and  the  process  is 
stopped  when  about  four-fifths  of  the  water  has  passed  over. 

110.  Physical  properties.  At  ordinary  temperatures, 
watQr  is  a  tasteless,  odorless  liquid.  When  seen  through 
a  depth  of  several  yards,  it  has  a  bluish  color.  It  is 
assumed  as  the  standard  for  specific  heat.  One  cubic 
centimetre  (Fig.  35)  of  distilled  water  at  4.1°  C.,  its  point 
of  greatest  density,  is  taken  as  the  unit  of  weight  in 
the  metrical  system.  This  unit  is  called  one  gramme  = 
15.4  grains.  At  this  temperature  it  is  taken  as  the 
standard  of  specific  gravity  for  solids  and  liquids. 


PROPERTIES  OF   WATER.  87 

The   freezing   and   boiling  points  of  water,  under  the 
pressure    of  one    atmosphere,    are    taken    as 
standards   of  temperature.     Water  freezes  to 
ice  at  a  temperature  of  0°  C.,  and  increases 
about  one-tenth  in  volume.     It  evaporates  at 
all   temperatures,   and   so   rapidly  at  100°  C.        FJG  3- 
that    it    is    said    to    boil.      Steam    at    100°  C. 
occupies  1696  times  the  volume  of  the  water  from  which 
it  was  formed. 

111.  Chemical  properties.  When  certain  crystals  are 
heated  they  give  off  water.  The  water  in  them  appears 
to  have  one  of  two  functions:  (1)  If  it  is  easily  ex- 
pelled by  heat,  it  forms  part  of  the  physical  molecule, 
and  is  called  the  water  of  crystallization;  (2)  if  it  re- 
quires considerable  heat  to  expel  it,  it  forms  part  of  the 
chemical  molecule,  and  is  called  the  water  of  constitution. 

Thus,  when  ferrous  sulphate  is  heated  to  114°  C.,  six  molecules 
of  the  water  of  crystallization  are  driven  oft'.  On  heating  to  280°  C., 
another  molecule  of  water  is  driven  off,  which  is  the  water  of  con- 
stitution. To  express  these  different  functions,  we  may  wrrite  the 
formula  of  ferrous  sulphate,  H2O,  FeO,  SO3  -f  6H2O. 

Some  anhydrides,  as  K2O  or  SO3,  so  firmly  unite 
with  water,  that  heat  alone  will  not  again  separate 
them:  K2O  -f  H2O  --=  2KHO;  SO3  -f  H2O  ==  H2SO4. 
These  bodies  are  collectively  spoken  of  as  hydrates,  and 
it  seems  probable  that  they  contain  water,  not  as  such, 
but  as  the  radical  hydroxyl,  K-IIO ;  (HO)'2  (SO2)". 
However,  some  hydrates  are  easily  decomposed  by  heat, 
as  Cu(HO)2,  which  changes  to  CuO -f  H2O. 

Many  organic  bodies,  like  starch,  C6H10O5,  contain 
hydrogen  and  oxygen  in  the  same  proportions  as  they 
are  found  in  water,  and  for  this  reason  have  been  called 
carbo-hydrates.  Nevertheless,  it  has  not  been  proved 
that  the  formula  of  starch  could  be  correctly  written 
06(H2O)5,  or  that  water,  as  such,  enters  into  its  mole- 


88  CHEMISTRY. 

cule.     Bodies  that  contain   neither  water   nor   hydroxj'l 
are  said  to  be  anhydrous,  as  KNO3,  or  P2O5. 

112.  Water  is   specially   useful   to   the   chemist    as    a 
solvent.     It  dissolves  a  large  number  of  bodies,  and,  on 
being   evaporated,  again   yields   them    unchanged.     The 
rain,  in  falling,  absorbs  many  atmospheric   constituents, 
and   afterward,  sinking    into    the    ground,  dissolves   the 
soluble   matters   of  the  soil.     If  this  water  again  comes 
to  the  surface,  as  spring  or  river  water,  it  contains  more 
or  less  solid   matters,  varying  with    the    nature    of  the 
rocks  through  which    the   water   flows.     The  ocean  and 
isolated  seas,  like  the  Caspian,  are   the   final   reservoirs 
of  rivers.     Their   waters    undergo  a  natural  distillation, 
yielding  pure  water  to  the  clouds,  and  become,  in  con- 
sequence, more   highly  charged    with    saline  matters,  or 
become  salt  water.     The  water  of  the  Great  Salt  Lake 
contains    12,000   grains    of  solid    matter    to    the    gallon. 
Sea   water   averages  about  2,000   grains   to   the   gallon. 
The  potable  waters  of  springs  and  rivers  seldom  contain 
as    high    as    100  grains  to   the  gallon,  and  many  lakes 
and  rivers  in  granitic  regions  are  very  nearly  pure. 

113.  The  wholesomeness  of  potable  waters  is  not  so 
much  dependent  on  their  mineral  as  upon  their  organic 
constituents.     If  water  contains  ten  grains  to  the  gallon 
of  organic    matters    in   a   state   of   decomposition,   it   is 
likely    to    be   very    unwholesome.     Kunning   waters   are 
self-purifying,  because  their  organic  impurities  are  con- 
tinually exposed  to  the  air  and  are  entirely  decomposed. 
Water  may  be  purified  for  drinking  purposes  by  filter- 
ing through  a  thick  layer  of  charcoal. 

Distilled  water  is  unpalatable,  or  "flat."  The  palata- 
bleness  of  water  depends  largely  on  its  gaseous  constit- 
uents. If  distilled  or  boiled  water  is  suffered  to  trickle 
through  the  air,  it  becomes  <;  aerated  "  and  more  pleasant 
to  the  taste. 


HYDROGEN  PEROXIDE.  89 

TESTS. — When  obtainable  in  large  quantities,  water  is  sufficiently 
known  by  its  physical  properties.  The  presence  of  water  in  mix- 
tures is  indicated  by  its  power  of  changing  white  anhydrous  cupric 
sulphate  to  a  blue  color.  The  anhydrous  cupric  sulphate,  CuSO4, 
is  easily  formed  by  gently  roasting  "  blue  vitriol." 

114.  Hydrogen  peroxide,  H2O2,  is  prepared  by  treating 
barium  peroxide  with-  dilute  hydrochloric  acid  : 

Ba02  +  2IIC1  =  BaCl2  +  II2O2. 

In  its  concentrated  form  it  is  a  syrupy  liquid,  having  a  specific 
gravity  of  1.452.  It  is  easily  decomposed  into  water  and  oxygen. 
It  possesses  remarkable  oxidizing  powers,  changing  black  lead  sul- 
phide into  white  lead  sulphate,  and  decomposing  potassium  iodide, 
like  ozone.  Hence,  this  reaction  may  also  be  used  as  a  test  for 
hydrogen  peroxide.  Still  more  remarkable  is  the  property  which 
it  has  of  inducing  other  peroxides,  when  mixed  with  it,  to  yield  a 
part  of  their  oxygen,  both  bodies  becoming  reduced  at  the  same 
moment.  Thus,  when  hydrogen  peroxide  is  poured  upon  manga- 
nese dioxide,  both  bodies  evolve  oxygen: 

Mn02  +  H202  =  MnO  -f  H2O  +  O~2. 
Recapitulation. 

Hydrogen    is    the    lightest   of   the    elements.      It    is    taken    as    the 
standard  unit: 

(1)  For  the  specific  gravity  of  gases. 

(2)  For  atomic  and  molecular  weights. 

(3)  For  molecular  volumes. 

(4)  For  atomicity,  or  unit  of  combining  power. 

The  basicity  of  an  acid  is  the  amount  of  hydrogen  it  contains  that 
may  be  replaced  by  a  metal. 

Hydrogen  also  seems  to  stand  midway  between  the  metals  and  the 
other  elements. 

Oxygen   is   the    most   abundant   element,    and    is  strongly   electro- 
negative! 
Its  compounds  are: 

Basic,  with  most  of  the  electro-positive  elements. 

Acid,  with  most  of  the  electro-negative  elements. 

Indifferent,  with  metallic  peroxides  and  H2O. 


90 


CHEMISTRY. 


Water  is  proved   to   have  the  formula  H2O,  both  by  analysis  and 
synthesis.     (Arts.  46  and  47). 

It  is  an  indifferent  body,  acting  — 

Basic,  with  negative  anhydrides;   as,  H2O,  SO3. 
Acid,  with  positive  anhydrides;    as,  K2O,  H2O. 

In  compounds,  it  may  be  regarded  as  present  — 

(1)  As  water  of  crystallization,  Na2B2O7  -f  10H2O. 

(2)  As  water  of  constitution,  H2O,  FeSO.t  -f  CII2O. 

(3)  Represented  by  its  radical  hydroxyl;  as,  K-HO;  (HO)2(SOa)". 


CIIAPTEE    V. 

THE    CHLORINE    GROUP    (HALOGENS). 


H 

O>    r-5 

IN   AERIFORM 

. 

^» 

STATE. 

^  M 

ELEMENT. 

u  w 

H  o 

§ 

a 

M  r  " 

SPECIFIC  GRAVITY. 

So 

23 

DISCOVERER. 

£  " 

>< 

oo 

£«    H? 

(CO  S 

AIR-  1. 

H-l. 

<£ 

Fluorine 

Gas           F 

1.31? 

19? 

19. 

Chlorine 

Gas 

Cl 

1.33 

2.47 

35.5 

35.5 

Scheele,    1774. 

Bromine 

Liquid 

Br 

2.96 

5.54 

80 

80 

Balard,     182G. 

Iodine 

Solid 

I 

4.95 

8.79 

127 

127 

Courtois,  1812. 

115.  These  four  elements  compose  a  natural  group, 
the  members  of  which  exhibit  a  gradation  of  similar 
properties.  They  are  all  found  in  minute  quantities  in 
sea  water  and  in  many  mineral  springs.  They  are  fre- 
quently called  the  halogens  (<5Uc>  the  sea),  because  they 
form  binary  compounds  resembling  scasalt ;  as,  NaF, 
NaCl,  NaBr,  Nal.  Such  compounds  are  called  the 
haloid  salts.  So,  also,  each  of  these  elements  combines 
with  an  equal  volume  of  hydrogen  to  form  an  acid 
which  is  called  a  haloid  acid.  These  acids  are  HF,  hy- 
drofluoric; HC1,  hydrochloric;  HBr,  hydrobromic;  HI, 


£  FLUORINE.  91 

hydriodic.  The  haloid  acids  are  gases  distinguished  by 
a  great  attraction  for  water,  and  readily  forming  with 
it  solutions  which  act  as  the  free  acids  would  act.  In 
these  compounds  they  are  monads  ;  but  they  seem  also 
to  act  as  triads,  pentads,  and  even  as  septads.  The 
halogens  are  never  found  native,  and  it  is  doubtful 
whether  fluorine  has  ever  been  isolated. 

The  last  three  are  liberated  in  the  aeriform  state  by  heating 
their  haloid  salts  with  a  mixture  of  manganese  dioxide  and  sul- 
phuric acid.  The  general  reaction  may  be  expressed  by  the  equa- 
tion for  chlorine: 

2NaCl  +  Mn02  +  2H2SO4  =  Na2SO4  -f  MnSO4  +  2H2O  +  2"C1. 

Their  chemical  energies  are  very  active.  The  general 
order  of  their  affinities  for  the  positive  elements  is  in- 
versely as  their  atomic  weights ;  their  affinities  for  oxy- 
gen increase  writh  their  atomic  weights.  Fluorine  is 
probably  an  incoercible  gas;  chlorine  is  a  yellowish  gas, 
liquefying  at  — 40°  C. ;  bromine,  a  red  liquid,  boiling  at 
63°  C. ;  and  iodine,  a  black  solid,  melting  at  115°  C.  and 
boiling  at  200°  C. 

FLUORINE. 

116.  The  most  abundant  compound  of  fluorine  is  fluor 
spar  (CaF2).     It  is  also  found  in  cryolite  (3NaF,  A1F8), 
in  many  other  minerals,  and  in  the  bones  and  the  teeth. 

117.  The  chemical  properties  of  fluorine  are  probably 
analogous  to  those  of  chlorine.     It  forms  no  compounds 
with    oxygen,    nor    with    any    others    of  the    non-metals 
except  hydrogen,  boron,  and  silicon. 

118.  Hydrofluoric  acid,  HF.     This  acid  is  liberated  in 
the  gaseous  state  when  powdered  fluor  .spar   is   treated 
with  twice  its  weight  of  strong  sulphuric  acid : 

CaF2  -f  H2SO4  =  CaSO4  +  2HF. 


92  CHEMISTRY. 

Anhydrous  hydrofluoric  acid  is  a  colorless,  volatile 
liquid  which  boils  at  19.4°  C.,  and  emits  dense  fumes 
at  ordinary  temperatures.  Both  the  gas  and  the  liquid 
are  readily  soluble  in  water.  The  commercial  acid  of 
sp.  gr.  1.15  has  the  formula  HF,  2II2O. 

The  acid  powerfully  corrodes  the  skin,  a  single  drop 
producing  a  painful  sore,  and  the  fumes  are  danger- 
ously irritating  to  the  lungs.  The  most  useful  property 
which  it  possesses  is  its  power  of  combining  with  silicon 
to  form  the  gaseous  fluoride  of  silicon  (SiF4).  Glass  is 
made  of  various  silicates,  as  silicate  of  soda  and  silicate 
of  lime  ;  hence,  hydrofluoric  acid  is  used  for  etching 
glass. 

Exp.  83.  —  Coat   a  glass   plate  with   a   thin    layer  of  wax,  and 
then,  by  means   of  a   sharp   point,  engrave   a  word  or  drawing  so 
that  its  lines  shall  expose  the  glass.     Place  the  waxed  surface  over 
u    leaden    dish   containing   a   mixture  of  fluor  spar 
and  sulphuric  acid.    Warm  the  dish  gently,  taking 
care    not   to    melt    the   wax.     In    a   few  hours   the 
glass    will   be   etched  l>y  the  gas.     The  liquid  HF, 
^H2O    may   also   be    used    for   etching    glass.     The 
white  crust  which  generally  forms  when    the   glass 
is  etched  by  gaseous    HF   is   silica.     This  comes   from    the   decom- 
position of  the  SiF4  by  the  water  which  is  obtained  from   the   sul- 
phuric acid. 

SiF4  +  2  H20  =  Si02  +  4  HF. 

119.  The  4HF  thus  liberated  combines  with  a  second 
portion  of  SiF4  to  form  2IIF,  SiF4,  hydro-fluo-silicic 
acid,  which  does  not  corrode  glass.  Hydro-fluo-silicic 
acid  forms  difficultly  soluble  salts  with  potassium  (2  KF, 
SiF4)  and  some  other  metals,  and  is  sometimes  used  to 
separate  these  elements  from  their  soluble  compounds. 


.  84.  —  Mix  5  grammes  of  fluor  spar  with  an  equal  quantity 
of  powdered  glass  or  clean  sand.  Put  the  mixture  into  a  Florence 
flask  furnished  with  a  wide  tube  dipping  into  mercury  in  the  receiver, 
and  add  30  grammes  of  strong  sulphuric  acid.  A  gentle  heat  evolves 


CHLORINE. 


93 


SiF4.    Now  pour  water  above  the  mercury  so  carefully  that  none 
shall  enter  the  tube.     As   the   SiF4  passes   through  the  water  it  is 
decomposed,  bubbles  coated  with  an  envelope  of  silica,  SiO2,  form, 
and    2  HF,  SiF4    remains    in 
solution.     The  silica  may  be 
filtered  off  through  linen,  and 
the    solution    of    hydro-fluo- 
silicic  acid  preserved  for  fut- 
ure use. 


CHLORINE. 

120.  Chlorine  is  a  con- 
stituent of  sodium  chlo- 
ride (common  salt)  and 
of  potassium  chloride, 
both  of  which  are  very 
abundant. 


FIG.  36. 


121.  Preparation.  Chlorine  may  be  conveniently  pre- 
pared by  gently  heating  manganese  dioxide  with  hydro- 
chloric acid. 

Mn02  +  4HC1  =  MnCl2  +  2H2O  +  Cl2. 

To  obtain  one  litre  of  chlorine,  about  20  grammes  of  the  acid 
and  6  grammes  of  the  dioxide  are  required. 

The  funnel  tube  shown  in  Fig.  37  answers  for  the  introduction 
of  the  acid  in  small  quantities,  and  also  as  a  safety  valve.  Heat 
should  not  be  applied  until  the  oxide  is  thoroughly  wetted  by  the 
acid.  The  gas  may  be  washed  by  passing  it  through  a  small 
quantity  of  water  in  B.  It  is  dried  by  passing  it  through  strong 
sulphuric  acid  in  C. 

If  the  dry  gas  is  wanted,  it  is  collected  by  downward  displace- 
ment, as  represented  in  Fig.  37.  The  color  of  the  gas  easily  shows 
when  the  jar  is  filled.  The  gas  may  then  be  kept  for  some  time 
in  the  jar,  if  the  stoppers  are  greased. 


122.  The  gas  can  not  be  collected   over   cold   water, 
because  water  at  10°  C.  absorbs   2.58   times   its   volume 


94 


CHEMISTRY. 


of  chlorine.     It  may,  however,  be  collected   over  warm 
water  or  brine. 


FIG.  37. 

Exp.  85. — To  prepare  a  solution  of  chlorine,  or  chlorine  water, 
fill  a  retort  with  distilled  water  and  place  it  in  the  position  shown 
in  Fig.  38.  Carry  a  long  delivery  tube  into  the  body  of  the  retort, 

so  that  the  chlorine  may  bubble 
through  the  water.  Shake  the 
retort  from  time  to  time,  and 
keep  it  cool  by  pouring  water 
on  the  outside.  The  operation 
may  be  stopped  when  the  bubbles 
of  gas  are  no  longer  absorbed. 

Chlorine  water  may  be  pre- 
served for  future  use  by  storing 
it  in  bottles  covered  with  black 
paper  and  kept-  in  a  cool  place. 
It  possesses  most  of  the  proper- 
FIG.  88.  ties  of  the  gas. 

123.  Physical  properties.  Chlorine  is  a  greenish  yel- 
low gas  of  pungent  odor.  It  is  one  of  the  heaviest 


CHEMICAL  PROPERTIES  OF  CHLORINE.  95 

gases,  being  2.47  times  heavier  than  air.  It  may  be 
condensed  at  12.5°  C.  to  a  yellow  liquid  (sp.  gr.  1.33), 
by  a  pressure  of  8.5  atmospheres;  but  it  has  never 
been  solidified,  even  at — 90°  (\ 

Exp.  86.— To  show  its  rapid  absorp- 
tion by  water,  hold  a  jar  of  chlorine  gas 
downward  in  water,  and  decant  one-third 
of  it.  Now  close  the  mouth  of  the  bottle 
with  the  hand,  and  shake  the  bottle. 
The  water  will  completely  absorb  the 
gas,  producing  a  vacuum  in  the  bottle, 
which  will  then  be  held  to  the  hand  FIG,  39. 

by  atmospheric  pressure. 

When  saturated  chlorine  water  is  cooled  to  0°  C., 
yellow  crystals  of  C1,5H2O,  chlorine  hydrate,  may  be 
obtained.  These  crystals  are  used  as  a  source  for  ob- 
taining liquid  chlorine. 

124.  The    chemical    properties    of   chlorine    are    very 
active,  and  give  rise  to  the  various  phenomena  of  com- 
bination,   displacement    and    substitution,    and    indirect 
oxidation. 

125.  (I)  Combination,     Very  nearly  all   the   elements 
unite  directly  with  chlorine.     O.  C.  F.  are  exceptions. 

Exp.  87. — Prepare  several  jars  of  the  dry  gas.  Powdered  an- 
timony sprinkled  into  the  chlorine  forms  SbCl5,  generally  evolving 
flashes  of  light.  A  similar  result  follows  by  using  powdered  me- 
tallic arsenic  or  bismuth. 

Exp.  88. — Place  in  a  deflagrating  spoon  a  piece  of  dry  phos- 
phorus, and  plunge  this  into  a  jar  of  the  gas.  The  two  elements 
combine  with  a  pale  flame  to  form  PC13  or  PC15.  (See  Fig.  29.) 

Exp.  89.— Stir  gold  leaf  in  chlorine  water.  It  soon  dissolves 
to  AuCl3. 

126.  (II)  Displacement   and   substitution.     The   most 


96 


CHEMISTRY. 


important  applications  of  chlorine  depend  on  its  affinity 
for  hydrogen. 

If  a  jet  of  burning  hydrogen  be 
introduced  into  a  jar  of  chlorine,  it 
will  continue  to  burn  with  the  forma- 
tion of  HC1.  A  mixture  of  the  two 
gases  combines  slowly  in  diffused  light, 
but  suddenly  and  with  explosive  force 
in  the  direct  sunlight.  (See  Exp.  56). 

Exp.  90. — Pour  chlorine  water  into 
a  solution  of  hydrogen  sulphide.  The 
latter  is  decomposed  with  precipita- 
tion of  sulphur,  and  hydrochloric  acid 
is  formed.  H,S  -f  2C1  =  2HC1  +  S. 

Exp.  01. — To  a  tube  two-thirds  full  of  chlorine  water  add 
enough  ammonia  solution  to  fill  it;  then  invert  the  tube  in  a 
capsule  of  water.  Bubbles  of  nitrogen  will  rise  to  the  top,  and 


hydrochloric  acid  will  be  formed:  NH3  -f  3  Cl  =  3  HC1  -f-N.'  The 
hydrochloric  acid  will  then  combine  with  another  portion  of  the 
ammonia  to  form  NH3HC1,  ammonium  chloride.* 

Exp.  92. — Wet   strips   of  filter   paper  with   ivarm  turpentine, 
and  plunge  into  a  jar  of  dry  chlorine.     The  tur- 
pentine will    be   decomposed;    its 
hydrogen  will  unite  with  chlorine, 
and  dense   fumes   of  carbon  will 
be  evolved,   as    carbon   does   not 
unite  directly  with  chlorine.  (Fig. 
41). 

Hence,    if    lighted     tapers    be 
plunged   into   chlorine   gas,  they 
burn  feebly  with  a  smoky  flame, 
FIG.  41.  only  the  hydrogen   of  the   taper 

combining  with  the  chlorine.    (Fig.  42). 

So,  also,  chlorine  will  decompose  water.  If  a  tube  filled  with 
chlorine  water  be  inverted  in  water  and  placed  in  the  sunlight, 
bubbles  of  oxygen  will  collect  at  the  top  of  the  tube.  The  hydro- 


*  Care  must  be  taken  to  keep  the  ammonia  in  excess;  otherwise,  a  very  ex- 
plosive compound,  nitrogen  chloride  (NHCU,  NC13),  will  also  be  formed. 


USES  OF  CHLORINE.  97 

chloric  acid  formed  dissolves  in  the  excess  of  water.  (See  Exps.  7 
and  28):    H2O  -f  2  Cl  =  2  HC1  +  ft 

127.  (Ill)    Indirect   oxidation.     The   last   experiment 
shows  that  chlorine  may  be  used  as  an  oxidizing  agent. 
When   so   used,   the   oxygen   liberated  is  applied  in  the 
nascent  state  and  is  very  energetic. 

Exp.  93. — Add  to  a  solution  of  manganous  sulphate  a  little 
potassium  hydrate:  white  manganous  oxide  precipitates.  Now  add 
a  few  drops  of  chlorine  water:  black  dioxide  of  manganese  im- 
mediately forms;  MnO,  II 2O  +  2  Cl  =,  MnO2  -f  2  HC1, 

128.  Uses.    (I)  Bleaching  properties.     Dye  stuffs  are  fre- 
quently   organic    compounds    containing    hydrogen.      If 
chlorine   acts  upon  such  dyes  in  the  presence  of  water, 
they  are  changed   to   colorless  compounds  as  the  result 
of  chlorination  or  of  oxidation.     Hence,  chlorine   is  an 
excellent  bleaching  agent. 

Exp.  94.— Place  strips  of  printed  calico  in  chlorine  water,  or 
expose  them  in  a  damp  state  to  the  action  of  the  gas.  Most  of  the 
colors  will  soon  disappear.  Indigo  first  oxidizes  to  isatin,  and  then 
changes  to  chlorisatin,  both  of  which  are  soluble  in  water  and  are 
nearly  colorless.* 

The  experiment  may  be  repeated  with  green  leaves  or  flowers. 
Most  mineral  colors  remain  unaltered.  Printers'  ink  is  not  affected 
at  all,  as  it  is  largely  carbon. 

(II)  Disinfecting  properties.  Among  the  noxious  prod- 
ucts of  the  decay  of  animal  and  vegetable  matters  are 
ammonia,  hydrogen  sulphide,  and  similar  compounds. 
Chlorine  acts  upon  these  compounds  in  the  same  way 
that  it  acts  upon  coloring  matters,  and  converts  them 
into  harmless  substances.  Hence  it  is  of  great  value  as 
a  disinfectant! 


*  C8H5NO  (indigo)  +  H2O  +  C12  =  C8H5NO2  (isatin)  +  2HC1. 
C8H5NO2  (isatin)  +  C12  =  C8H4C1NO2  (chlorisatin)  +  HC1. 
Chem.— 7. 


98 


CHEMISTRY. 


TESTS. — Free  chlorine  may  be  recognized,  (1)  by  its  odor,  (2) 
by  its  bleaching  properties,  and  (3)  by  its  producing  a  blue  color 
in  acting  upon  a  mixture  of  starch  and  potassium  iodide  (Exp.  28). 

129.  Hydrochloric  acid,  HC1.     Discovered  by  Priestley. 

Preparation.  —  Introduce    about    20    grammes    of    fused    sodium 

chloride  into  a  flask,  and  pour 
over  it  40  grammes  of  sulphuric 
acid.  Heat  the  flask  very  gently, 
and  collect  the  gas  by  displace- 
ment in  dry  jars.* 

130.    Physical   properties. 

Hydrochloric  acid  is  a  col- 
orless gas,  having  an  acid 
taste  and  pungent  odor.  It 
has  a  specific  gravity  of  1.27, 
and  may  be  condensed  by  a 
pressure  of  40  atmospheres 
to  a  colorless  liquid.  At  15° 
C.,  one  volume  of  water  ab- 
sorbs 400  times  its  volume  of  the  gas. 


FIG.  43. 


Exp.  95. — Its  solubility  in  water 
may  be  shown  by  fitting  to  a  bottle 
containing  the  gas  a  cork  furnished 
with  a  glass  tube,  and  inverting  the 
bottle  over  water.  In  a  short  time 
the  water  will  rush  into  the  bottle  as 
if  into  a  vacuum. 

The  commercial  acid,  frequently 
called  muriatic  acid,  is  made  by  pass- 
ing the  gas  into  a  series  of  bottles 
containing  cold  water.  (Fig. 45).  When 
this  acid  has  a  specific  gravity  of  1.21, 
it  contains  43  per  cent,  by  weight,  of 
HC1,  and  may  be  represented  by  the 
formula,  HC1  +  3H2O. 


FIG.  44. 


2  NaCl  +  H8SO4  -  Na2SO4  +  2  HC1. 


HYDROCHLORIC  ACID. 


99 


131.  Chemical  properties.  Hydrochloric  acid  dissolves 
many  metals  and  their  oxides,  forming  with  them  chlo- 
rides which  are  represented  by  KC1,  FeCl2,  and  Fe2Cl6. 
All  of  the  metallic  chlorides  are  soluble  in  water  except 
AgCl,  Hg2Cl2,  PbCl2,  T1C1,  and  Cu2Cl2.  When  hydro- 
chloric acid  acts  upon  an  oxide,  two  atoms  of  chlorine 
are  required  to  displace  one  atom  of  oxygen.  Thus  : 

FeO  +  2HC1  =  FeCl2  +  H2O. 


Fe2O 


6HC1  •=  Fe2Cl6 


3H2O. 


When  no  chloride  so  corresponding  to  the  oxide  exists, 
part  of  the  chlorine  is  set  free  and  a  lower  chloride 
formed.  This  is  generally  the  case  with  the  peroxides  ; 
as,  Mn02,  Pb02;  PbO2  -f  4HCl  =  PbCl2  +  2H2O-f  <fta. 

TESTS.  —  HC1  gas  forms,  with  the  vapor  of  ammonia,  white  fumes 
of  KE3,  HC1.  Solutions  of  HC1,  or  of  the  metallic  chlorides,  yield, 
with  silver  nitrate,  a  white,  curdy  precipitate,  AgCl,  soluble  in 
ammonia,  but  insoluble  in  nitric  acid. 


FIG.  45. 


132.  Uses.  Enormous  quantities  of  hydrochloric  acid 
are  evolved  in  the  manufacture  of  soda.  This  acid  is 
used  as  a  source  of  chlorine  in  the  manufacture  of  cal- 


100  CHEMISTRY. 

cium  hypochlorite.     In  the  laboratory  it   finds   constant 
employment  as  a  convenient  solvent. 

133.  The  compounds  of  chlorine  and  oxygen.    Chlorine 
forms   ther  following   series   of  acids,  which   may  be  re- 
garded as  formed  from  an  anhydride,  with  the  addition 
of  one  molecule  of  water,  or  as  oxides  of  hydrochloric  acid. 

WATER.     ANHYDRIDE.          NAME  OF  ACID.  HC1. 

H2O,  -f  C12O    :=  hypochlorous  acid,  2  X  HC1O. 
H2O,  -f  C12O3  =  chlorous  acid,  2  X  HC1O2. 

H20,  +  C1206  =  chloric  acid,  2  X  HC1O3. 

H2O,  -f  C12O7  =  perchloric  acid,        2  X  HC1O4. 

Only  the  first  two  anhydrides  have  been  isolated. 
The  acids  are  seldom  prepared.  They  are  very  unstable, 
and  are  liable  to  produce  dangerously  explosive  com- 
pounds. Besides  these,  there  exists  chloric  peroxide, 
CI2O4,  for  which  no  corresponding  acid  is  known. 

134.  Hypochlorites.     The    best    known    hypochlorites 
are   sold   under   the   names   of  "  chloride   of  lime "   and 
"  chloride  of  soda."    These  are  mixtures  which  owe  their 
useful  properties  to  the  calcium  hypochlorite,  CaO,  C12O, 
and  sodium  hypochlorite,  Na2O,  C12O,  which   they  con- 
tain.     They   are    excellent    bleaching    and    disinfecting 
agents.     Hypochlorous  acid  is  itself  more  energetic  than 
chlorine,  probably  because,  on  breaking   up,   it   evolves 
chlorine  and  oxygen,  both  in  their  nascent  state. 

"We  may  study  its  properties  by  means  of  a  solution 
prepared  from  good  "chloride  of  lime." 

Exp.  96. — Add  to  a  little  of  the  solution  an  equal  amount  of 
dilute  nitric  acid.  Yellow  fumes  will  be  given  off,  which  are  hypo- 
chlorous  acid. 

Exp.  97. — Repeat  the  experiment,  using  an  excess  of  sulphuric 
or  hydrochloric  acid.  Only  chlorine  will  be  liberated. 

Exp.  98. — Place  in  each  of  the  preceding  mixtures,  and  also  in 
a  fresh  quantity,  paper  which  has  been  written  upon,  and  notice  the 
relative  rapidity  with  which  each  is  bleached. 


CHLORATES. 


Exp.  99. — Add  a  few  drops  of  the  solution  to  a  solution  of 
manganous  chloride  or  of  cobaltous  nitrate;  the  black  precipitates 
which  fall  are  MnO2  or  Co2O3.  The  protoxides  have  acquired 
additional  oxygen  from  the  calcium  hypochlorite. 

Exp.  100. — Add  a  few  drops  of  cobaltous  nitrate  to  a  pint  of 
the  solution,  and  heat.  A  large  quantity  of  oxygen  will  be  given 
off,  which  may  be  collected  and  tested.  The  cobaltic  oxide  seems 
to  act  as  a  carrier  of  the  oxygen,  first  combining  with  it  and  then 
giving  it  off. 

135.  The  hypochlorites  are  prepared  by  passing  chlo- 
rine through  or  over  the  metallic  hydrates. 

Exp.  101. — Pass  a  slow  current  of  chlorine  gas  into  a  cold 
dilute  solution  of  potassium  hydrate.  The  solution  acquires  strong 
bleaching  properties  from  the  formation  of  potassium  hypochlorite. 

2  (K2O,  H20)  -f  4  Cl  =  K20,  C12O  +  2  KC1  +  2  H2O. 

136.  The  chlorates.     If  this  solution  be  boiled,  it  will 
be  converted  into  potassium  chloride  and  potassium  chlo- 
rate: 3(K2O,  C12O)  =4KC1+K2O,  C12O5  or  2(KC1O8). 

Exp.  102. — Pass  a  rapid  stream  of  chlorine  gas  into  a  mod- 
erately strong  solution  of  potassium 
hydrate.  The  liquid  will  soon  be- 
come hot  enough  to  decompose  the 
hypochlorite,  and  the  ultimate  result 
will  be  thus  expressed: 


K20,  C1205  -j-  10KC1  +  6  H20. 

If  the  solution  be  allowed  to  cool, 
tabular  crystals  of  potassium  chlorate 
will  be  deposited.  If  the  solution  be 
then  poured  off,  and  the  crystals  re- 
dissolved  in  boiling  water,  a  second 
crop  of  crystals  may  be  obtained,  FIG.  45. 

which  are  nearly  pure  potassium  chlorate. 

137,  Chloric  acid,  H2O,  C12O5  or  HC1O3.     If  a  solution 
of  potassium    chlorate   be    mixed  with  hydro  -fluo-silicic 


CHEMISTRY. 

acid,  potassium  silico-fluoride  is  deposited,  and  hydrated 
chloric  acid  remains  in  the  solution. 

K20,  C1205  +  2HF,  SiF4  =  2 KF,  SiF4  +  H2O,  C12O5. 

This  solution  concentrated  in  vacua  yields  a  syrupy, 
yellow  liquid  of  peculiar  odor.  It  inflames  paper,  sul- 
phur, and  phosphorus  —  sometimes  with  explosive  vio- 
lence. The  acid  and  its  salts  are  easily  decomposed  by 
heat  and  by  the  stronger  acids,  and  are  among  the  most 
energetic  oxidizing  agents  known. 

Exp.  103.  — Powder  separately  equal  weights  of  sugar  and  po- 
tassium chlorate,  and  then  mix  the  powders  carefully.  The  mix- 
ture, touched  with  a  glass  rod  dipped  in  sulphuric  acid,  burns  with 
a  brilliant  white  light. 

Exp.  104. — A  little  of  the  sugar  mixture,  wrapped  in  paper 
and  struck  by  a  hammer,  detonates  violently.  If  half  of  the  sugar 
is  replaced  by  dried  potassium  ferro-cyanide,  it  forms  "white  gun- 
powder." 

Exp.  105. — Potassium  chlorate  forms  with  sulphur  or  phos- 
phorus detonating  compounds.  If  a  very  I'dtlc  sulphur  be  rubbed 
in  a  mortar  with  potassium  chlorate,  frequent  explosions  will  take 
place. 

138,  Chloric  peroxide  and  chlorous  acid  are  dangerous 
to  prepare  on  account  of  their  ex- 
plosive character. 

Exp.  106. — Drop  a  few  crystals  of 
potassium  chlorate  into  a  glass  of  water 
containing  a  few  small  slices  of  phos- 
phorus. Now,  by  means  of  a  pipette,  add 
a  little  sulphuric  acid  to  the  bottom  of 
the  glass.  A  yellow  gas,  chloric  peroxide 
(C12O4  or  C1O2),  is  formed,  and  oxidizes 
the  phosphorus  with  bright  flashes  of  light 
FIG.  47.  and  slight  detonations. 

Exp.  107. — Add  a  few  crystals  of  potassium  chlorate  to  hydro- 
chloric acid,  and  warm  gently  if  no  action  immediately  ensues. 
A  yellow  gas  called  euchlorine  is  evolved.  It  has  very  energetic 


BROMINE.  103 

bleaching  and  oxidizing  properties,  and   is   probably  a  mixture   of 
chlorine  with  anhydrous  chlorous  and  chloric  acids. 

139.  Potassium  perchlorate  is  formed  when  potassium 
chlorate  is  gently  heated  until  the  mass  becomes  pasty. 
One-third  of  the  oxygen  is  given  off,  and  the  remainder 
is   a   mixture  of  potassium  chloride  and  potassium  per- 
chlorate:  2(K2O,  C12O5)  ==  K2O,  C12O7  -f  2KC1  +  O4. 
If  this  mass  is  dissolved  in  hot  water,  and  the  solution 
allowed  to  cool,  potassium   perchlorate   crystallizes   out. 
Perchloric  acid  may  be  obtained  from  this  salt  by  pre- 
cipitating the  potassium  by  hydro-fluo-silicic  acid  (§137). 

The  perchlorates  do  not  yield  C12O4  when  treated 
with  sulphuric  acid.  They  have  no  commercial  uses. 

TESTS. — These  experiments  are  also  tests  for  the  compounds  of 
oxygen  and  chlorine.  When  heated,  they  are  all  converted  to 
chlorides,  and  may  then  be  tested  as  such. 

BROMINE. 

140.  Bromine   occurs   in    the   waters   of  many   saline 
springs  and  in  sea  water.     When  such  liquids  are  evap- 
orated, most   of  the   other  salts  crystallize  out, 

and  the  liquid  remaining  ("  bittern ")    contains 
magnesium  and  sodium  bromides.* 

141.  Preparation.     These    liquids   are   treated 
with  chlorine,  the  bromine  is  set  free,  and  the 
vapors  which   escape   are   collected   in  a  cooled 
receiver.     These  consist  of  liquid  bromine  and 
an  aqueous  solution  of  bromine. 

Exp.    108.— Add    chlorine    water   to    a    solution    of 
potassium  bromide.    Bromine  will  separate  out  and  render        FIG.  48. 
the  liquid  yellowish  red.    Place  this  liquid  in  a  separatory 
funnel  (Fig.  48),  and  add  a  little  ether.    Shake  the  mixture  and  then 
allow  it  to  stand.    An  ethereal  solution  of  bromine  will  rise  to  the  top. 

142.  Physical    properties.     At    15°  C.,    bromine    is   a 

*  Nearly  200,000  pounds  of  bromine  are  made  in  Ohio  annually. 


104  CHEMISTRY. 

dark  red  liquid  of  a  disagreeable  odor,  from  which  it 
derives  its  name  (^pojfjLO^  a  stench) :  sp.  gr.  2.96.  It 
solidifies  at  — 22°,  boils  at  63°  C.,  and  yields  abundant 
vapors  at  ordinary  temperatures.  It  is  sparingly  soluble 
in  water;  readily  in  ether  and  in  carbonic  disulphide. 

143.  Its  chemical  properties  are  like  those  of  chlorine. 
It   has   a   strong   affinity   for    hydrogen,    and,    therefore, 
may  be    used    as    an    agent   for    indirect   oxidation,    for 
bleaching,  and  for  disinfecting. 

Exp.  109. — Vaporize  a  few  drops  of  bromine  in  a  jar,  and 
introduce  a  pellet  of  dry  phosphorus.  PBr3  is  formed,  with  evolu- 
tion of  light. 

With  other  jars  test  its  bleaching  properties,  etc.,  as  with  Cl. 

TESTS. — Free  bromine  is  recognized  by  its  odor,  and  by  the 
orange  color  it  gives  to  a  starch  solution. 

The  bromides  give,  with  silver  nitrate,  yellowish  white  silver 
bromide,  AgBr,  which  is  converted  by  chlorine  water  into  AgCl 
and  free  Br.  The  Br  may  be  separated  by  shaking  with  ether. 

144.  Uses.     The    bromides    are    used    in    photography 
and  in  medicine.     Free  bromine  is  used  in  some  chem- 
ical operations  in  preference  to  chlorine. 

Bromine  forms  HBr  (hydrobromic  acid),  H2O,  Br2O 
(hypobromous  acid),  and  H2O,  Br2O5  (broinic  acid), 
which  resemble  the  corresponding  chlorine  compounds. 


IODINE. 

145.  Iodine  is  contained   in   sea  water   in  exceedingly 
minute  quantities.     Certain   marine   plants  and   animals 
contain    it   in    such    proportions  that  it  can  be  obtained 
from  their  ashes  with  profit. 

146.  Preparation.     The  ashes  of  sea  weed,  called  kelp, 
are    treated    with    a   little    hot  water,   and   the   solution 
which    forms   is   set    aside   to    crystallize.     The   mother 


IODINE. 


105 


liquors  contain  sodium  iodide,  Nal.  These  liquors,  heated 
with  manganese  dioxide  and  sulphuric  acid,  evolve  free 
iodine,  which  is  collected  in  cooled  receivers.  The  iodine 
may  also  be  isolated  by  chlorine.  (Exps.  19  and  28). 

147.  Physical  properties.     Iodine  is  a   grayish   black, 
crystalline    solid.     It    volatilizes    at    ordinary    tempera- 
tures,  melts   at   115°  C.,   and 

boils  at  200°  C.,  evolving  the 
beautiful  vapors  from  which 
it  derives  its  name  (iwdyz, 
violet-colored). 

It  dissolves  in  7,000  parts 
of  water;  readily  in  aqueous 
solutions  of  metallic  iodides, 
in  alcohol,  ether,  and  chloro- 
form. Its  best  solvent  is  car- 
bonic disulphide. 

Exp.    110. —  (1)     Volatilize    a 

grain  of  iodine  in  a  dry  flask:  (2)  after  the  sublimate  has  cooled, 
dissolve  it  in  a  few  drops  of  alcohol:  (3)  add  water,  and  most  of 
the  iodine  will  precipitate:  (4)  shake  a  little  of  the  aqueous  solu- 
tion in  a  test  tube  with  ten  drops  of  carbonic  disulphide.  On 
standing,  the  disulphide  will  settle  to  the  bottom  of  the  tube,  and 
its  color  change  to  violet,  owing  to  the  dissolved  iodine. 

148.  The  chemical  properties   of  iodine  are  less  ener- 
getic  than   those   of  chlorine    and    bromine.     Either    of 
these    elements    displaces    it   from    its    haloid    salts.     Its 
bleaching   powers   are    very    feeble.     We    have    already 
seen  that  it  unites  directly  with  other  elements.    (Exps. 
10,  11,  12,  15).     It  acts  corrosively  upon  organic  tissues, 
staining  the  skin  yellow. 

TESTS. — Free  iodine  forms  a  beautiful  blue  color  with  starch 
paste,  and  a  violet  solution  with  CS2. 

The  iodides  give,  with  silver  nitrate,  a  buff-colored  Agl;  with 
mercuric  chloride,  scarlet  HgI2.  Any  iodide  treated  with  chlorine 


106 


CHEMISTRY. 


yields    free   iodine,  which  may  then    be   tested    with   starch   paste. 
An  excess  of  chlorine  should  be  avoided. 

The  iodine  may  also  be  set  free  by  potassium  nitrite  acidulated 
with  acetic  acid. 

149,  Uses.     Iodine  is  largely  used  in  the  manufacture 
of  aniline  green  and  in  photography.     The  element  and 
its   salts   are   employed    in   medicine,  especially  for  the 
treatment  of  enlarged  glands. 

150.  Hydriodic   acid,  HI.     Free  hydrogen  and  iodine 
do  not  readily  unite ;    but,  when   iodine  is  present  with 
nascent  hydrogen,  the  two  elements  unite  to  form  hydri- 
odic  acid. 

This  is  illustrated  by  Exp.  31.  Nevertheless,  hydriodic  acid  is 
a  very  unstable  body.  It  is  readily  decomposed  by  the  oxygen 
of  the  air,  forming  water  and  depositing  iodine.  It  may  even  act 
as  a  reducing  agent.  In  the  experiment  just  cited,  it  is  necessary 
that  the  solution  of  sulphurous  acid  be  very  dilute,  for,  otherwise, 
considerable  sulphuric  acid  is  formed,  and  is  again  reduced  by  the 
hydriodic  acid  to  sulphurous  acid. 

H2S04  +  2  HI  =  H2S03  +  HaO  +  2 1. 

A  solution  of  hydriodic  acid  is  con- 
veniently prepared  by  passing  hydrogen 
sulphide  through  water  containing  iodine 
in  suspension:  H2S  -f  2 1  =  S  -f  2  HI. 
The  separated  sulphur  is  filtered  off,  and 
the  solution  warmed  to  expel  the  excess 
of  hydrogen  sulphide. 

151.  Oxides  of  iodine.  Iodine 
has  a  much  stronger  affinity  for 
oxygen  than  either  chlorine  or 
bromine.  lodic  acid,  H2O,  I2O5, 
may  be  obtained  by  heating  iodine 
with  strong  nitric  acid  in  a  flask, 
to  which  is  fitted  a  long  glass 
tube  that  serves  to  condense  the  iodine  which  volatilizes 
unchanged.  By  heating  this  to  170°  C.,  iodic  anhydride, 


FIG.  50. 


IODATES.  107 

I2O5,  may  be  obtained.  "At  about  370°  it  is  decomposed. 
The  acid  forms  iodates  which  closely  resemble  their  cor- 
responding chlorates. 

There  exist,  also,  periodic  acid,  H2O,  I2O7,  and  other 
compounds  whose  composition  has  not  been  determined 
with  certainty. 


Recapitulation. 

The  halogens  are  volatile  elements  which  usually  act  as  electro- 
negative monads. 

Fluorine  is  characterized  by  a  wonderful  affinity  for  silicon. 

Cl,  Br,  and  I  form  a  natural  group  whose  relations  to  each  other 
are  more  intimate  than  are  those  of  any  one  of  them  to  F. 

All  combine  readily  with  hydrogen,  forming  acids  which  are  exceed- 
ingly soluble  in  water.  Cl  decomposes  water  rapidly  in  the  sun- 
light. Br  slowly,  and  I  not  at  all. 

By  reason  of  this  affinity  for  hydrogen,  Cl  and  Br,  in  the  presence 
of  H2O,  act  indirectly  as  oxidizing,  bleaching,  and  disinfect- 
ing agents.  HI  is  easily  decomposed,  and  is  an  important 
reagent  in  organic  chemistry  as  a  source  of  nascent  iodine. 

All  combine  directly  with  most  metals  to  form  haloid  salts.  The 
most  common  in  nature  are  those  containing  Na,  K,  Ca,  or  Al. 

The  haloid  salts  are  frequently  associated  together  in  nature,  and 
are  generally  isomorphous. 

They  tend  to  form  double  salts,  as  2KI,  HgI2.  This  is  especially 
characteristic  of  the  salts  of  fluorine,  as  2  KF,  SiF4. 

Fluorine  forms  no  compounds  with  oxygen. 

The  oxy-salts  of  the  others  are  easily  decomposed,  yielding  the 
haloid  salt  and  free  oxygen.  Hence,  the  oxy-salts  may  be 
used,  either  alone  or  with  strong  acids,  as  oxidizing  agents. 


CHAPTER    VI. 

THE    SULPHUR    GROUP. 


s 

SPECIFIC  GRAVITY. 

og 

o  . 

ELEMENT. 

« 

SOLID.          VAPORS. 

S3 

h 

DISCOVERER. 

03  £ 

5 

H2O=  1. 

AIR=  1. 

<£ 

£2 

Sulphur 

s 

2.05 

2.21 

32. 

120° 

Selenium 

Se 

4.79 

5.48 

79.5 

250° 

Berzelius,  1817. 

Tellurium 

Te 

6.65 

8.91 

129. 

500° 

Klaproth,  1798. 

Oxygen 

0 

1.106 

16. 

Priestley,   1774. 

152.  A  natural  gradation  of  properties   is  also  exhib- 
ited   by    this    group.     Their   specific   gravities,    melting 
points,   and  atomic   weights    form   an   increasing  series. 
Their  chemical  energies  are  in  a  reverse  order,  sulphur 
being  the  most  active  and  tellurium  the  least. 

They  are  each  characterized  by  forming  fetid  aeriform 
compounds  containing  two  volumes  of  hydrogen  to  one 
of  the  other  element — the  three  volumes  condensing  to 
two;  as,  II2S, H2Se.  In  this  respect,  oxygen  is  allied 
to  this  group,  as  also  in  the  fact  that  each  of  them  is 
capable  of  replacing  oxygen  in  most  of  its  compounds, 
atom  for  atom.  Hence,  they  are  generally  ranked  among 
the  dyad  elements;  but  they  also  form  compounds  in 
which  they  are  quadrivalent,  as  SC14,  and  sexivalent, 
as  S(C2H4)"(C2H6y2Br'2.  Their  highest  atomicity, 
therefore,  classes  them  as  negative  hexads. 

153.  Each  element   of  this   group  forms  two  acid  an- 
hydrides   with    oxygen,  and    at    least   two   acids,  which 
have  similar  formulas  and  properties, 

(108) 


SULPHUR. 


109 


^ 

Type,  2H20  or  y2>O2 

ANHY- 
DRIDES 

"  OUS  "  ACIDS 

A  N  H  Y- 
DKIDES 

"  1C  "  ACIDS 

H2S 

H2Se 
H2Te 

SO2 
Se02 
TeO2 

H2O,  SO2     or  H2SO3 
H20,Se02  or  H2SeO3 
H2O,TeO2  or  H2TeO3 

S03 
Se03* 
Te03 

H2O,  SO3     or  H2SO4 
H20,Se03  or  H2SeO, 
H2O,  TeO3  or  H2TeO4 

The  hydrogen  of  each  of  these  compounds  is  replace- 
able by  two  atoms  of  a  monad  metal  or  by  one  atom 
of  a  dyad,  to  form  corresponding  salts;  as,  K2S,  K2SO4, 
CaS,  CaS04. 

154.  The   physical    properties   of   tellurium   ally   this 
group  to  the  metals.     It  conducts   heat   and   electricity, 
though    not  readily,  and   has  a  brilliant  metallic  luster. 
Sulphur  is  a  non-conductor   of  heat   and   of  electricity, 
and    has    a    vitreous    luster.     Selenium,   a   red   solid,   is 
midway  between  them.    Finally,  all  three  occur  native, — 
selenium   frequently   associated  with   sulphur,  tellurium 
associated  with  gold  and  other  metals. 

NOTE. — Lately  an  ore  of  gold  has  been  found  in  Colorado  combined  with  con- 
siderable quantities  of  tellurium  ;  but  tellurium  and  selenium  are  still  so  rare 
as  to  need  no  further  description. 

SULPHUR. 

155.  Sulphur  is  found  native  in  considerable  quantities. 
It   occurs   in   many   minerals   as   sulphides — e.  g.,    iron 
pyrites    (FeS2),    copper    pyrites    (Cu2S,  FeS2),    galena 
(PbS),    blende    (ZnS),    cinnabar    (HgS) ;     and    as    sul- 
phates—e.   <?.,  gypsum   (CaSO4),    heavy   spar   (BaSO4), 
Epsom   salts    (MgSO4),    and   Glauber's   salts    (Na2SO4). 
It   is   also   a  constituent  of  many  organic  products,  as 
casein,  fibrin,  albumin,  and   the   oils  of  cruciferous  and 
alliaceous  plants,  as  mustard  and  garlic. 


*  Selenic  anhydride  has  not  been  isolated. 


110 


CHEMISTRY. 


156,  Preparation.     In  order  to  free  it  from  its  earthy 
impurities,  native   sulphur  generally  requires  to  be  dis- 
tilled. 

The  vapors  are  conducted  into  large  brick  chambers,  and  are 
there  condensed.  The  flowers  of  sulphur  are  the  first  product  ob- 
tained while  the  walls  of  the  chamber  are  yet  cold.  After  a  time, 
the  walls  of  the  chamber  become  heated;  the  sulphur  melts  and  is 
cast  into  wooden  moulds  to  form  roll  sulphur  or  brimstone. 

157.  Physical   properties.     Sulphur  is  a  brittle,  yellow 
solid,  tasteless  and  almost  inodorous.     On  being  heated, 
it  becomes  a  limpid  fluid  at  120°  C. :  as  the  temperature 
rises,  it   darkens   and   thickens,  until,  at  about  250°  C., 
it  is  so  viscid  that  the  vessel  in  which   it   is   contained 
may  be   inverted   without   spilling   it:   above  300°  C.  it 

again  liquefies,  boils  at  440° 
C.,  and  is  converted  into  an 
orange  vapor,  which,  at  500° 
C.,  has  a  density  of  96,  and 
at  1000°  C.,  the  normal  den- 
sity of  32. 


If,  now,  the  vessel  is  removed 
from  the  flame,  and  a  small  quan- 
tity is  poured  into  cold  water,  it 
forms  an  amorphous,  elastic  mass 
called  plastic  sulphur.  The  por- 
tion remaining  in  the  vessel  passes, 
as  it  cools,  through  the  viscid  and 
limpid  states,  and  finally  crys- 
tallizes in  oblique  prisms.  If  the  liquid  portion 

be   poured   off  as   soon  as  a  crust  has  formed  on 

the  surface,  the  crystals  will  be  found  lining  the 

interior  walls. 

If,    now,    some    of  the    crystals    are    dissolved 

in  carbonic  disulphide,  and  the  solution  is  allowed 

to  evaporate   spontaneously,  beautiful   octahedral 

crystals  are  deposited,  resembling  those  of  native 

sulphur. 

Plastic   sulphur  is  not  soluble  in  carbonic  disulphide. 


FIG.  52. 


CHEMICAL  PROPERTIES  OF  SULPHUR.         Ill 

158.  Sulphur  has,  then,  at  least  three  allotropic  states : 
(1)  the  octahedral,  (2)  the  oblique  prismatic,  and  (3)  the 
plastic.     The   milk    of  sulphur  is  another  modification, 
obtained  by  precipitating  sulphur  from  the  alkaline  poly- 
sulphides   by   the   addition   of  acids.     All   of  these  are 
changed  to  the  prismatic  form   by   fusion,   and  all,  on 
standing,  assume  more   or   less   perfectly  the  octahedral 
condition. 

Exp.  111. — Confirm  these  facts  by  performing  the  operations 
indicated.  A  test  tube  will  suffice  to  show  the  changes  assumed 
by  heating;  but,  to  obtain  fine  oblique  prisms,  a  good-sized  crucible 
is  required. 

159.  Chemical   properties.     Sulphur  enters  into  direct 
combination  with  many  of  the  elements. 

Exp.  112. — Heat  in  a  test  tube  a  mixture  of  sulphur  with  twice 
its  weight  of  copper  filings.  The  two  elements  unite  with  vivid 
combustion  at  a  temperature  a  little  above  the  melting  point  of 
sulphur.  (See  also  Exp.  14). 

The  compounds  with  the  metals  are  sulphides.  These 
have,  in  general,  properties  and  formulae  analogous  to 
their  corresponding  oxides,  as  FeS,  CuS. 

Carbonic  disulphide,  CS2,  is  formed  by  passing  the  vapor  of  sul- 
phur over  ignited  coals.  (See  §  305). 

Sulphur  heated  in  the  air  inflames  at  250°  C.,  and  burns  with  a 
pale  blue  flame,  being  converted  into  sulphurous  anhydride,  SO2, 
and  evolving  peculiar,  suffocating  fumes,  the  same  as  are  noticed 
in  burning  matches  coated  with  sulphur. 

160.  Tests.     Free  sulphur  is  recognized  by  its  physical 
properties  and  by  its  peculiar  odor  when  burned. 

Sulphur  in  combination  may  be  detected  by  (1)  placing  in  a 
small  tube  of  very  thin  glass  a  little  magnesium  or  sodium:  (2) 
covering  the  metal  with  the  substance  to  be  tested,  which  must  be 
perfectly  free  from  water;  and  (3)  then  heating  the  mixture  in  the 
flame  of  a  lamp.  A  vivid  combustion  ensues,  and  a  sulphide 
(hepar)  is  formed.  (4)  On  bringing  this  sulphide  upon  a  bright 


112  CHEMISTRY. 

silver  coin,  and  moistening  the  mass  with  water,  a  black  stain 
(Ag2S)  will  be  produced  on  the  silver  if  sulphur  is  present. 

The  hepar  may  also  be  made  by  fusing  a  substance  which  con- 
tains sulphur  upon  coal,  with  sodium  carbonate,  before  a  flame  free 
from  sulphur. 

161.  Uses.     Large    quantities    of  sulphur  are   used   in 
preparing   its    numerous  compounds,    as   sulphuric  acid, 
etc.,  in  vulcanizing  India  rubber,  and  in  making  matches 
and  gunpowder. 

162.  Hydrogen   sulphide,  also  called  sulphuretted  hy- 
drogen  and   hydrosulphuric  acid,  H2S,  occurs  native  in 
"  sulphur    springs,"    and    is    one    of  the    causes    of  the 
odors  of  putrefying  organic  substances,  as  of  rotten  eggs. 

163.  Preparation.    Hydrogen  sulphide  is  generally  pre- 
pared by  decomposing  ferrous  sulphide  with  dilute  sul- 
phuric acid :    FeS  +  II2O,  8O3  =  FeO,  8O3  +  II^S. 

The  process  is  similar  to  that 
described  in  Ex  p.  23.  Fig.  53 
exhibits  an  apparatus  which  is 
convenient  when  small  quantities 
of  the  gas  are  wanted  from  time 
to  time.  A  bit  of  glass  tubing, 
made  funnel-shaped  at  one  end, 
contains  the  ferrous  sulphide.  It 
is -supported  by  a  cleft  cork  in 
FIG.  53.  the  large  cylinder,  which  contains 

the  dilute  acid.     When  the  tube 

is  pushed  down  into  the  cylinder,  the  acid  enters  through  the 
mouth  of  the  funnel,  and  the  reaction  begins.  It  may  be  stopped 
by  lifting  the  tube  out  of  the  acid.  The  smaller  cylinder  contains 
a  little  water,  in  order  to  wash  the  gas. 

164.  Physical  properties.     Hydrogen  sulphide  is  a  col- 
orless, coercible  gas  of  extremely  offensive  odor :  sp.  gr. 
1.178.     At   ordinary  temperatures,  water   absorbs   about 
three  times  its  volume  of  the  gas. 


HYDROGEN  SULPHIDE.  113 

165.  Chemical   properties,     The  gas  is  readily  inflam- 
mable, and  burns  with  a  blue  flame  like  that  of  sulphur. 
Its  solution  is  readily  decomposed  by  chlorine,  bromine, 
or  iodine,  by  many  oxidizing  agents,  and  even  by  pro- 
longed contact  with  the  air.     In  such  cases  the  sulphur 
is  generally  deposited,  and  the  hydrogen  unites  with  the 
chlorine,  oxygen,  etc.     Hence,  it  may  act  as  a  reducing 
agent. 

Exp.  113. — Add  a  few  drops  of  calcium  hypochlorite  to  a  solu- 
tion of  hydrogen  sulphide.  The  "  milk  of  sulphur  "  is  deposited. 

CaCla02  -f  2H2S  =  CaCl2  +  2  H2O  +  S2. 

Exp.  114. — Acidulate  a  solution  of  potassium  bichromate  with 
sulphuric  acid,  and  then  add  hydrogen  sulphide.  On  warming  the 
solution  a  green  color  appears,  which  indicates  the  production  of 
chromic  sesquioxide: 

K20,  2  Cr03  -f  4  H2O,  SO3  +  3  H2S  = 

K20,  S03  +  Cr203,  3  SO3  -f  7 H2O  -f  3  S. 

Chromic   anhydride    is    reduced   to   chromic  sesquioxide,  and  ferric 
salts  to  ferrous  salts: 

2CrO3  +  3H2S  =  Cr2O3  +  3H,O-f  S3; 
Fe2Cl6  +  H2S  =  2  FeCl2  +  2  HC1  +  S^~ 

166.  Uses.     Besides  this  reducing  action,  it  is  largely 
employed  in  the  laboratory  as  a  group  reagent. 

I.  It  precipitates  from  their  solutions  Hg,  Pb,  Ag,  Cu,  Cd,  Bi, 
as  sulphides^  insoluble  in  dilute  acids  or  in  alkaline  sulphides. 

II.  It  precipitates  from  solutions  feebly  acid  As,  Sb,  Sn,  Au,  Pt, 
as  sulphides,  which  act  as  sulpho-acids,  and  combine  with  the  alka- 
line   sulphides    to    form    sulpho-salts    that    are    soluble    in    water. 
Hence,  these  elements  are  not  precipitated  in  alkaline  solutions. 

III.  The  sulphides  of   Ni,   Co,   Fe,   Mn,  Zn,  U,    are   soluble  in 
dilute  acids;  hence,  they  are  precipitated  only  in  alkaline  solutions 
or  by  alkaline  sulphides. 

IV.  Aluminium  and  chromium  do  not  form  sulphides  in  the  wet 
way,  but  are  precipitated  as  oxides-  by  the   alkalies  in  presence  of 
hydrogen  sulphide. 
Chem.— 8. 


114  CHEMISTRY. 

V.  The  sulphides  of  the  more  electro-positive  elements,  as  Mg,  K, 
are  easily  soluble  in  water,  and,  hence,  are  not  precipitated  by  H2S. 

Exp.  115. — Arrange  five  test  glasses  to  represent  these  groups. 
Pour  a  solution  of  arsenious  acid  into  I,  of  lead  nitrate  into  II, 
ferric  chloride  into  III,  alum  into  IV,  potassium  hydrate  into  V, 
and  pass  a  current  of  the  gas  into  each  of  these.  Yellow  As2S3 
will  form  in  I;  black  PbS,  in  II;  white  S,  in  III,  from  a  reduc- 
tion of  Fe2Cl6  to  FeCl2;  and  no  apparent  reaction  will  take  place 
in  the  others.  Now  add  a  little  of  V  to  the  As2S3 — it  redissolves;  to 
the  PbS — it  is  unchanged;  to  a  fresh  solution  of  ferric  chloride — 

black  FeS  precipitates;  to  alum — white 
A12O3,  3H2O  falls.  Add  ammonia 
to  III  and  IV:  the  same  change 
occurs  as  in  the  last  two  examples. 

TESTS.  —  Hydrogen    sulphide    may 

II      ill     iv      v  k    recognized  by  its  odor  and  by  its 

FIG   54 

reactions  upon  members  of  group  I. 

Strips  of  "  lead  paper,"  made  by  dipping  unsized  paper  into  a  so- 
lution of  lead  acetate,  are  very  useful  for  this  purpose.  The  alka- 
line sulphides  strike  a  purple  color  with  sodium  nitro-ferro-cyanide, 
even  in  very  dilute  solutions. 

167.  Physiological  properties.     The  gas  is  exceedingly 
poisonous  when  breathed,  and,  even  when  much  diluted, 
it  gives  rise  to  nausea  and  vertigo. 

168.  The   compounds    of  sulphur   and    oxygen.     Two 

anhydrides  of  sulphur  have  been  isolated — sulphurous 
anhydride,  SO2,  and  sulphuric  anhydride,  SO3.  They 
each  combine  with  one  molecule  of  water  to  form  sul- 
phurous acid,  H2O,  SO2,  and  sulphuric  acid,  H2O,  SO3. 
These  are  of  great  use  in  the  arts.  There  exists,  also, 
a  series  of  acid  compounds  containing  more  than  one 
atom  of  sulphur,  which  are  known  collectively  as  the 
polythionic  series  (Oseou,  sulphur).  Of  this  series,  only 
the  thiosulphates  are  of  commercial  importance. 

The  acid  compounds  may  be  arranged  as  follows.  Several 
formulae  are  given  of  each,  to  illustrate  different  methods  of 
notation. 


THE  SULPHUR  ACIDS.  115 

I.  MONOTHIONIC  SERIES. 

O  =  S<**H   or  H'(SO)"(OH)'  or  H2O,SO(?)  or  H2SO2. 

Hydrosulphurous  or  hyposulphurous  acid.*" 
0  =  S<^  or  (SO)"(OH/2  or  H2O,  SO2  or  H2SO3. 

Sulphurous  acid. 

—  S<nS  or  (SOa)"(OH)'a  or  H2O,  SO3  or  H2SO4 
O  — 

Sulphuric  acid. 

II.  POLYTHIONIC  SERIES. 

0^S<OH  °r  (HS)/  (S°2)//  (OH)/  °r  H'°'S2°2  or  H2S203. 
Hyposulphurous  or  thiosulphuric  acid.* 

III. 
S09—  OH  S02—  OH         S—  S02—  OH  S—  SO2-OH 

s<  I  s< 

S02—  OH  S02—  OH  S—  S02—  OH  S—  SO2—  OH 

or  or  or  or 

H2S206  H2S306  HaS406  H2S506 

Dithionic  acid.  Trithionic  acid.  Tetrathionic  acid.  Pentathionic  acid. 


169,  All  these  acids  are  dibasic  ;  that  is,  their  hydro- 
gen may  be  exchanged  for  one  dyad  or  for  two  monad 
atoms.     If  both   hydrogen  atoms  are  thus  replaced,  the 
salt  is   normal,   as   K2SO4,  potassium  sulphate;   if  only 
one  hydrogen  atom  is  replaced  by  a  monad,  the  salt  is 
acid,  as  KHSO4,  acid  potassium  sulphate,  or  bisulphate 
of  potassa.     If  two   different  metals   take   the  place   of 
the    hydrogen,    the    resulting   salt   is   double,  as  K'2Cu" 
(S04)2  +  6JE20. 

170,  Sulphurous   anhydride,   SO2,   is   found  in  nature 
among  the  gases  issuing  from  volcanoes.     No  considera- 

*A  lamentable  confusion  exists  in  the  names  of  the  first  and  fourth.  By 
strict  analogy,  salts  of  the  first  should  be  called  hyposulphites,  as  Na2SO2  ;  but 
long  use  has  given  salts  of  the  fourth  acid;  as  Na2S2O3,  the  name  hyposulphites, 
and  it  is  difficult  to  change  u  name  which  has  become  familiar.  They  should  be 
called  thiosulphates. 


116 


CHEMISTRY. 


ble  quantity  is  found  in  the  air  of  towns,  although  it 
must  be  continually  evolved  in  the  burning  of  coals 
which  contain  sulphur. 

171.  Preparation.  Sulphurous  anhydride  is  the  sole 
product  of  the  combustion  of  sulphur  in  oxygen.  It  is 
generally  prepared  for  laboratory  purposes  by  heating 
strong  sulphuric  acid  with  either  mercury  or  copper. 


2(H2O,  SO3)  +  Cu  =  CuO, 


2H2O 


Exp.  116.—  Heat  in  a  flask  20 
grammes  of  copper  clippings  with 
60  cc.  (Fig.  35)  of  strong  sulphuric 
acid.  Collect  a  portion  of  the  gas 
by  displacement  in  dry  cylinders, 
and  then  form  a  solution  of  the 
gas  by  passing  it  into  water. 
(Fig.  55).  When  the  operation  is 
finished  and  the  flask  is  cooled, 
there  will  he  found  a  grayish 
powder  at  the  bottom  of  a  brown 
liquid.  Decant  the  liquid,  add  a 
little  water  to  the  powder,  boil, 
and  filter.  After  a  little  while, 
crystals  of  blue  cupric  sulphate 
will  be  formed  in  the  filtrate.  Often  there  remains  on  the  filter  a 
dark  powder  which  is  insoluble  in  water:  this  is  a  sulphide  of 
copper,  formed  by  the  complete  reduction  of  the  sulphuric  acid. 

(a)  H2O,  SO3  -f  4  Cu  =  CuS  -f  H2O  +  3  CuO. 

(V)   3  CuO  +  3  (H2O,  SO3)  =  3  (CuO,  SO3)  -f  3  H2O. 

172.  Physical  properties.  Sulphurous  anhydride  is  a 
colorless,  easily  coercible  gas  of  a  pungent,  suffocating 
odor:  sp.  gr,  2.25.  It  condenses,  at  —  10°  C.,  to  a 
colorless  fluid,  which  solidifies  at  —  79°  C:  sp.  gr.  1.49. 

Exp.  117.  —  Pass  the  gas  from  the  flask  in  which  it  is  generated, 
(1)  into  an  empty  bottle  surrounded  by  ice,  in  order  to  cool  it; 
then  (2)  through  a  chloride  of  calcium  tube,  to  dry  it;  and  (3) 
into  a  U  tube  surrounded  by  a  mixture  of  ice  and  salt.  (Fig.  66). 


SULPHUROUS  ACID.  117 

Sulphurous  anhydride  condenses,  and  may  be  preserved  in  sealed 
tubes  or  in  soda  water  bottles. 

Liquid  sulphurous  anhy- 
dride produces,  by  its  evap- 
oration, cold  so  intense  as 
sometimes  even  to  freeze 
itself.  It  freezes  water 
readily,*  and  mercury  if 
the  evaporation  is  assisted 
by  a  brisk  current  of  air.  FIG,  5f>. 

Water  at  15°  0.  absorbs 

45  times  its  volume  of  the  gas,  forming  sulphurous  acid, 
H2O,  SO2.  On  freezing  this  solution,  a  crystallized 
hydrate  is  obtained,  which  is  thought  to  have  the  for- 
mula H2SO3,  14H2O. 

173.  Chemical  properties.     Sulphurous  anhydride  rap- 
idly  extinguishes    the    flame    of  ordinary    combustibles. 
If  a  pan  of  burning  sulphur  is  placed  at  the  base  of  a 
chimney  on  fire,  the  flame   of  the   burning   soot   is   ex- 
tinguished.    Nevertheless,  many  metals   in   a   finely  di- 
vided state  burn  when  heated  in  an  atmosphere  of  this 
gas. 

A  solution  of  sulphurous  acid  exposed  to  the  air 
slowly  takes  up  oxygen  and  becomes  sulphuric  acid. 
This  tendency  to  absorb  oxygen  renders  the  acid  and 
its  salts  powerful  reducing  agents.  (See  Exp.  31). 

Exp.  118. — Add  a  few  drops  of  sulphurous  acid  to  a  weak 
solution  of  potassium  permanganate.  The  red  color  disappears. 

174.  Sulphurous   acid   is   an  excellent  bleaching  agent 
for  wool,  silk,  and  straw.     The  bleaching  is  not  always 
permanent,  since  the  acid  does  not  seem   to    decompose 
the    coloring    matters,    but    to    form    unstable,    colorless 
compounds  with    them ;    as,  in  course  of  time,  the  color 
reappears. 

*See  Norton's  Philosophy,  Art.  577. 


118  CHEMISTRY. 

Exp.  119. — Add  a  little  sulphurous  acid  to  a  decoction  of  red 
cabbage  previously  rendered  green  by  a  drop  of  potassium  hydrate: 
the  color  disappears.  Now  divide  the  liquid  into  two  portions:  to 
the  first,  add  potassium  hydrate — the  green  reappears;  to  the  second, 
add  sulphuric  acid — the  liquid  becomes  red. 

Exp.  120. — Place  in  a  bell  glass  a  bunch  of  damp  flowers 
over  a  crucible  containing  burning  sulphur.  (Fig.  57).  Many  of 
the  flowers  will  be  bleached.  On  dipping 
some  of  them  afterward  into  sulphuric  acid, 
and  others  into  ammonia,  their  colors  will  be 
partly  restored,  but  generally  modified,  by 
the  action  of  the  acid  or  of  the  alkali. 


175.   Sulphurous  acid   and   its   salts 
are  valuable  antiseptics ;  that  is,  they 
have  the  power  of  preventing   or   of 
FlG  ry7>  arresting  fermentation.     For  this  rea- 

son eider  barrels  are  "  sulphured,"  in 
order  to  prevent  the  action  of  any  substance  capable 
of  exciting  fermentation  in  the  new  cider.  For  a  similar 
reason  calcium  sulphite  is  frequently  added  to  sweet 
cider.  The  air  of  rooms  may  be  disinfected  by  burning 
sulphur  in  them. 

TESTS. — Free  sulphurous  acid  is  readily  recognized  by  its  odor. 
The  sulphites  evolve  S02  when  treated  with  dilute  sulphuric  acid. 
If  zinc  be  added  to  this  mixture,  the  SO2  is  reduced  to  H2S, 
which  may  be  recognized  by  blackening  lead  paper. 

176.  Uses.     Sulphurous   acid    is   used  for  its  bleaching 
and    antiseptic    properties.      The    acid    sodium    sulphite, 
NaII,SO8,    is    used    by   paper    makers    as    an    antichlore, 
to    prevent    a    destruction    of  the   fiber   through    an    ex- 
cessive action  of  chlorine  in  bleaching. 

177.  Sulphuric    anhydride,    SO3,    niay   be    formed    by 
passing   a   mixture   of  dried   sulphurous   anhydride    and 
oxygen    through    a    tube    containing    heated    platinum 
sponge.      It    is    prepared    more    conveniently    from    the 
Kordhausen  oil   of  vitriol.     On  gently  heating  this,  the 


SULPHURIC  ACID.  119 

anhydride  is  disengaged,  and  may  be   collected   in   dry 
receivers  cooled  by  ice. 

178.  Physical   properties.     Sulphuric    anhydride   crys- 
tallizes   in   white,   feathery  groups   resembling   asbestos. 
When   perfectly  dry  it   may  be  handled  without  incon- 
venience, and  does  not  exhibit  acid  properties.     Exposed 
to  the  air  it  absorbs  water  and  becomes  sulphuric  acid. 
It  is  then  very  corrosive.     Dropped  into  water  it  hisses 
like  red-hot  iron. 

179.  Chemical  properties.     The  vapor  of  sulphuric  an- 
hydride  passed    over   heated    baryta    or    lime    converts 
these  bases  into  sulphates,  with  vivid  incandescence. 

180.  Sulphuric    acid,    H2O,  SO3  ==  H2SO4,    has   been 
found  free  in  certain  mineral  waters,  notably  so  in  the 
Rio   Vinagre   of  South   America.     It  results,  also,  from 
the  oxidation  of  sulphur  and  hydrogen  sulphide. 

181.  Preparation.    Sulphuric  acid  is  prepared  in  enor- 
mous quantities  by  the   oxidation   of  sulphurous  anhy- 
dride in  the  presence  of  water. 

Exp.  121.  —  Plunge  into  a  jar  of  sulphurous  anhydride  a  glass 
rod  which  has  been  dipped  in  fuming  nitric  acid.  Ked  fumes 
appear,  which  show  that  the  nitric  acid  has  been  reduced.  In  a 
little  while  the  red  color  disappears,  and  a  crystalline  substance 
forms  on  the  sides  of  the  jar.  Now,  if  a  little  water  be  shaken  on 
the  sides  of  the  jar,  the  crystals  dissolve  with  effervescence,  the  red 
fumes  again  appear,  and  the  water  contains  sulphuric  acid. 

Exp.  122.  —  This  process  may  be  repeated  on  a  larger  scale  by 
the  apparatus  shown  in  Fig.  58.  A  is  a  large  globe  fitted  with  a 
cork  through  which  are  passed  five  tubes,  three  of  which  are  con- 
nected with  the  generating  flasks,  a,  b,  c. 

I.  The  flask,  b,  contains  copper  filings.  On  pouring  a  very  little 
nitric  acid  on  these,  nitric  oxide  is  formed: 


3  Cu  +  4  (H20,  N205)  =  3  (CuO,  N2O5)  +  $O2  +  4  H2O. 


120  CHEMISTRY. 

II.  When   this   nitric   oxide   is    mixed  with  the  air  of  the  flask 
and  of  the  globe,  it  forms  red  fumes  which  are  nitrogen  peroxide: 

N2O2  -f-  air  or  oxygen  =  N2O4. 

III.  When  the  globe  is  filled  with  the  nitrogen  peroxide,  evolve 
sulphurous   anhydride    from    the    flask,    a,    containing    copper    and 
strong  sulphuric  acid. 


FIG.  58. 

IV.  The   sulphurous    anhydride    will   soon    reduce   the   nitrogen 
peroxide  to  nitric  oxide,  the  contents  of  the  globe  becoming  color- 
less:   2SO2 +  N2O4=2SO3 +N2O2.     The   crystalline   compound 
forms  on  the  side  of  the  flask.     The   structure   of  these  crystals  is 
unknown,  but  we  may  assume  them  to  be  N2O2,  2SO3. 

V.  Now  let   steam  be   passed   into   the   globe  from  the  flask,  c, 
which  contains  water.     The  crystals  effervesce,  and  dilute  sulphuric 
acid  collects  at  the  bottom  of  the  globe. 

N202,  2  S03  -f  2  H20  =  2  (H2O,  SO3)  +  N2O2. 

The  process  is  now  finished.  To  render  the  process  continuous, 
air  must  be  blown  from  time  to  time  through  the  tube,  d,  into  the 
globe.  The  N2O2  liberated  by  the  last  reaction  again  becomes 
N204.  Hence,  but  very  little  nitric  oxide  is  necessary  for  the 
production  of  a  large  amount  of  sulphuric  acid.  It  acts  as  a  car- 
rier of  oxygen  from  the  air  to  the  sulphurous  anhydride.  The 
tube,  e,  allows  the  nitrogen  of  the  air  to  escape. 


PROPERTIES  OF  SULPHURIC  ACID.  121 

It  is  scarcely  necessary  to  mention,  if  these  different  steps  occur 
simultaneously,  that  none  of  the  crystalline  compound  will  be  de- 
posited, as  it  is  at  once  decomposed  in  the  presence  of  water. 

In  sulphuric  acid  manufactories,  the  glass  globe  is  replaced  by  a 
series  of  enormous  leaden  chambers.  The  sulphurous  acid  is  gen- 
erated by  burning  sulphur  or  iron  pyrites  in  a  furnace  so  arranged 
that  the  proper  quantity  of  air  may  enter  the  chambers  with  the  sul- 
phurous anhydride.  The  nitric  acid  vapor  is  evolved  from  a  mixture 
of  sodium  nitrate  and  sulphuric  acid  contained  in  an  iron  pan,  which 
is  heated  by  the  combustion  of  the  sulphur.  Jets  of  steam  are  in- 
troduced at  various  parts  of  the  chambers,  and  water  is  allowed  to 
cover  the  floors.  The  sulphurous  anhydride  reduces  the  nitric  acid, 
and  combines  with  oxygen  and  water  to  form  sulphuric  acid.  Pro- 
vision is  made  to  allow  the  nitrogen  of  the  air,  which  takes  no 
part  in  these  changes,  to  escape,  and,  at  the  same  time,  to  prevent 
loss  by  absorbing  the  nitrogen  oxides  for  future  use. 

The  acid  is  allowed  to  collect  in  the  chambers  until  it  has  a 
specific  gravity  of  1.55.  It  is  then  drawn  off  and  evaporated  in 
leaden  pans  until  it  reaches  the  specific  gravity  of  1.72.  Farther 
concentration  is  effected  in  platinum  stills. 

The  commercial  acid  has  a  specific  gravity  of  1.82, 
and  is  known  as  oil  of  vitriol.  This  oil  of  vitriol  fre- 
quently contains  lead,  arsenic,  and  other  impurities. 

182.  Physical  properties.  Pure,  concentrated  sulphuric 
acid  is  an  oily,  colorless,  inodorous  liquid,  having  the 
specific  gravity  of  1.842.  It  boils  at  327°  C.,  and  solid- 
ifies at — 35°  C.  It  is  remarkable  for  its  great  attraction 
for  water. 

Exp.  123. — Place  four  ounces  of  water  in  a  beaker,  and  pour 
into  it  a  pint  of  strong  sulphuric  acid  in  a  thin  stream.  The  tern- 
perature  often  rises  to  100°  C.  If  the  mixture  be  stirred  with  a 
thin  test  tube  containing  alcohol,  the  alcohol  will  boil. 

When  exposed  to  the  air,  sulphuric  acid  will  often 
double  its  weight  in  a  few  days;  hence  it  is  often  used 
as  a  desiccating  agent. 

Gases  are  dried   by  allowing  them   to   pass    over   pumice   stone 


122  CHEMISTRY. 

soaked  in  strong  sulphuric  acid,  or  through  a  bottle  containing  the 
acid.  Other  bodies  are  dried  by  placing  them  in  shallow  vessels 
over  a  dish  of  sulphuric  acid,  and  covering  the  whole  by  a  bell 
glass  so  as  to  exclude  the  air.  By  conducting  this  operation  in 
vacua,  water  may  be  frozen  by  its  own  evaporation. 

183.  Chemical  properties,    Sulphuric  acid  also  abstracts 
water  from  many  organic  substances,  charring  them  or 
giving  rise  to  new  compounds. 

Exp.  124. — Drop  a  lump  of  sugar  into  strong  sulphuric  acid: 
in  a  short  time  it  will  become  carbonized. 

Organic  tissues  moistened  with  the  dilute  acid  are 
destroyed,  from  the  gradual  concentration  of  the  acid 
by  evaporation. 

Strong  sulphuric  acid  is  reduced  to  sulphurous  acid 
when  heated  with  charcoal,  sulphur,  or  the  ordinary 
metals.  The  metals  are  thereby  converted  to  oxides 
which  form  sulphates  with  another  portion  of  the  acid 
(Exp.  116).  On  the  other  hand,  metals  'of  the  zinc  and 
iron  groups,  except  copper,  when  treated  with  the  dilute 
acid,  displace  the  hydrogen  to  form  their  sulphates  (§81). 
The  sulphates  are  also  formed  when  the  acid  is  made  to 
act  upon  metallic  oxides,  or  upon  their  compounds  with 
nearly  all  other  acids.  The  acid  is,  therefore,  one  of 
the  most  energetic  known. 

TESTS. — Free  sulphuric  acid  and  solutions  of  its  salts  give,  with 
barium  chloride,  a  white,  insoluble  precipitate.  Similar  precipitates 
are  given  by  strontium  chloride  and  calcium  chloride. 

184.  Uses.     Sulphuric  acid  is  used  in  the  preparation 
of  most  other  acids,  in   the   manufacture  of  soda,  phos- 
phorus,   and    alum,   and    is    employed,   directly  or  indi- 
rectly, in    nearly  all    important   chemical    processes.     It 
is  the  most  important  chemical  reagent  we  have.     Over 
100,000   tons  are   annually   consumed    in    Great    Britain 
alone. 


THIOSULPHURIC  ACID.  123 

185.  Nordhausen  oil  of  vitriol  is  obtained  by  heating 
dried  ferric  sulphate  in  earthen  retorts.    The  acid  which 
distills  over  is  probably  a  compound  of  sulphuric  anhy- 
dride and  sulphuric  acid:    SO3H2SO4  —  H2S2O7. 

186.  Properties.     Nordhausen    acid   fumes    in    the    air 
when  the  bottle  containing  it  is  opened.     It   is   a   little 
heavier   than    the    ordinary   acid,    and    is    usually    of  a 
brownish  color.     Its  salts  are  sometimes  called  anhydro- 
sulphates,  as  K2S2O7. 

187.  Uses.     It  is  used  in  making  artificial  alizarine,  and 
for  dissolving  indigo  in  preparing  Saxony  blue. 

188.  Thiosulphuric  acid,  H2S2O3,  has  not  been  isolated. 
Its  salts  are  generally  known  as  hyposulphites. 

Sodium  hyposulphite  is  prepared  by  boiling  sodium 
sulphite  with  sulphur. 

Na20,S02+S  =  Na20,S202  or  Na2S2O8. 

It   may  be  obtained    in   prismatic   crystals,   having    the 
formula  Na2S2O3,  5H2O. 

Sodium  hyposulphite  is  used  for  preparing  other  hypo- 
sulphites, and  finds  extensive  employment  in  "fixing" 
photographic  prints. 

Exp.  125. — Prepare  a  little  silver  chloride  by  adding  hydro- 
chloric acid  to  silver  nitrate,  and  wash  with  water  by  decantation. 
To  one  portion,  suspended  in  water,  add  sodium  hyposulphite. 
The  silver  chloride  will  change  to  silver  hyposulphite,  and  dissolve: 
2  AgCl  -f  Na2S2O3  =  2  NaCl  -f  Ag2S2O3.  Expose  another  portion 
to  the  sunlight;  it  darkens  from  the  formation  of  a  silver  sub- 
chloride.  On  treating  this  with  sodium  hyposulphite,  the  silver 
subchloride  is  decomposed  into  silver  chloride,  which  dissolves  as 
before,  and  into  metallic  silver,  which  is  left  in  a  very  finely 
divided  state  as  a  black  powder.  The  photographer  repeats  this 
last  process,  except  that  he  performs  the  operation  upon  paper 
which  has  been  impregnated  with  silver  chloride,  and  completes 
the  process  by  washing  out  all  the  hyposulphite,  so  as  to  leave 
only  the  silver  which  has  been  reduced.  (See  $  398). 


124  CHEMISTRY. 

TEST. — The  hyposulphites  treated  with  hydrochloric  acid  evolve 
sulphurous  anhydride,  and  deposit  yellow  sulphur. 

189,  Haloid  compounds  of  sulphur.  Sulphur  forms 
compounds  with  chlorine,  bromine,  and  iodine.  One 
of  these  compounds — the  disulphide  of  chlorine,  C12S2— 
is  employed  as  an  agent  in  vulcanizing  caoutchouc.  It 
is  a  liquid  formed  by  passing  chlorine  through  the 
vapor  of  sulphur. 

Comparison  of  Oxygen  and  Sulphur. 

I.  Oxygen  and  sulphur  combine  directly  with  most  of  the  elements 

to  form  anhydrides. 

Basic  oxides;  as,  K2O.  Basic  sulphides;  as,  K2S. 

Indifferent  oxides;  as,  MnO2.    Indifferent  sulphides;  as,  FeS2. 
Acid  oxides;  as,  As2O3.  Acid  sulphides;  as,  As2S8. 

II.  The  anhydrides  may  unite  together,  forming — 
Oxy-salts;  as,  K2O,  As2O3.       Sulpho-salts;  as,  K2S,As2S3. 

III.  They  may  also  combine  with  H2O  or  with  H2S  to  form — 
Hydrates;  as,  K2O,  H2O.  Sulpho-hydrates;  as,  K2S,  H2S. 

Heat  alone  decomposes: 

The  oxides  and  sulphides  of  the  noble  metals;    as,  PtO2,  PtS2. 
Many  of  the  higher  oxides  and  sulphides;  as,  I2O5,  I2S2. 
And  reduces  some;  as,  MnO2  to  Mn3O4,  and  FeS2  Fe3S4. 

Hydrogen    nascent,   or    passed    over    heated    oxides   and  sulphides, 
reduces  many  of  them. 

CuO-f-H2  =Cu  +  H2O.  Ag2S  +  H2  =2Ag -f  H2S. 

Heated  carbon  reduces  the  oxides  and  sulphides  of  most  metals. 
Fe203  +  3  C  =  Fe2  +  3  CO.        2  FeS  +  C  =  2  Fe  +  CS"2. 

Chlorine  may  also  decompose  them,  uniting  with  the  more  electro- 
positive element. 
H20  +  C12  =  2  HC1  +  a  H2S  +  C12  =  2  HC1  -f  S. 


CHAPTER    VII. 

THE    NITROGEN    GROUP. 


J 

SPECIFIC  GRAVITY. 

0H 

p 

o  . 

ELEMENT. 

8 

SOLID.              AERIFORM. 

RC5 

-  £ 

DISCOVERER. 

a 

^  E2 

95  S 

>• 

H20  =  l. 

AIR  =  1. 

H  —  1. 

<E 

E£ 

Nitrogen 

N 

0.969 

14 

14. 

Kutherford,  1772. 

Phosphorus 

P 

1.83 

4.29 

62 

31. 

440 

Brandt,         1669. 

Vanadium 

y 

5.5 

51.3 

SefstrOm,       1830. 

Arsenic 

As 

5.73 

10.34 

150 

75. 

180° 

Schroder,      1694. 

Antimony 

Sb 

6.7 

244? 

122 

450° 

Valentine,  71480. 

Bismuth 

Bi 

9.9 

210 

264° 

Agricola,       1529. 

Niobium 

Nb 

6.27 

94. 

Hatchett,      1801. 

Tantalum 

Ta 

10.78 

182 

Ekeberg,       1802. 

190.  The  members  of  this  group  yield  analogous  com- 
pounds, as  exhibited  in  the  following  schedule : 


HYDRIDES, 
CHLORIDES, 


.  H3N, 

•  NCI,, 
rN203, 


ANHYDRIDES,  | -^  Q 


H3P, 
PC13, 
P203, 


H3As, 

AsCL, 


H3Sb. 

SbCl3,     BiCl3. 

Sb,Oq,    Bi0OQ. 


As2O5,    Sb2O5, 


Bi205. 


191.  The  hydrides  are  fetid,  inflammable  gases,  in 
which  three  atoms  of  hydrogen  are  united  with  one 
atom  of  the  other  element,  and  condensed  to  two  vol- 
umes. No  hydrides  of  vanadium  or  bismuth  are  known, 
but  there  exists  a  complete  series  of  trichlorides.  These 
compounds  indicate  that  the  elements  of  this  group  are 
triads ;  but  they  also  play  the  part  of  pentads  in  a 
number  of  compounds,  and  hence  are  variously  classed 
by  chemists  as  triad  and  as  pentad  elements.  All  of 

1125) 


126  CHEMISTRY. 

these    elements    form    at    least    two    compounds    with 
oxygen. 

192.  Vanadium  is  quite  rare.     It  has  chlorides  which 
are    both    perissads    and    artiads,    as    VC12,    VC13,    and 
VC14, —  which    is   an    unexplained    anomaly.      Niobium, 
sometimes    called    columbium,    and    tantalum    are    still 
rarer  elements. 

NOTE.— All  these  agree  in  forming  oxides  of  the  formula  R2OM  and  other 
compounds  which  place  them  in  this  group.  They  are,  however,  not  of  sufficient 
importance  to  be  considered  further. 

193.  The    other   elements   of  the   group   manifest  the 
gradational    character   noticed  in   the  preceding  groups. 
Nitrogen    and     phosphorus    are,    without    doubt,    non- 
metals  :    bismuth  presents  all  the  physical  characters  of 
the  metals :  arsenic  and  antimony  may  be  considered  as 
semi-metals,  or  as  a  connecting  link  between   the   non- 
metals  and  the  metals.    They  have  many  of  the  physical 
properties  of  the  metals  and  the  chemical  properties  of 
the  non-metals.     Arsenic   very   closely   resembles   phos- 
phorus  in    its   oxygen    compounds,  and  antimony  in  its 
sulphides    and    in    its    physical    properties.      Its    atomic 
weight  is  also  very  nearly  the   mean   between    the   two 
others.     Similarly,  antimony  is  allied  on  the   one   hand 
to  phosphorus,  and  on  the  other  to  bismuth. 

The  sesquioxides  of  this  group  are  acid  anhydrides  in 
nitrogen,  phosphorus,  and  arsenic,  feebly  acid  or  feebly 
basic  in  antimony,  and  basic  in  bismuth.  The  highest 
oxides  are  all  acid  anhydrides,  but  the  acid  properties 
of  bismuthic  oxide  are  very  feeble. 

NITROGEN. 

194.  Nitrogen   forms   four-fifths   of  the  volume  of  the 
air.     The    air   also   contains   traces   of  ammonia,   NH3. 
It  is  found  in  most  animal  and  in  many  vegetable  sub- 


NITROGEN.  127 

stances.     It  also  occurs  in  the  form  of  sodium   and   po- 
tassium nitrates,  and  of  the  ammoniacal  salts. 

195.  Preparation.     Nitrogen  may  be  obtained  from  the 
air  by  potassium   pyrogallate  (Exp.  78),  or  by  burning 
in  it  any  substance  which  forms  with  oxygen  a  product 
that  may  easily  be  removed. 

Exp.  126. — Place  a  dried 
slice  of  phosphorus  in  a  capsule; 
float  it  on  the  surface  of  water, 
and  ignite  it.  Now  cover  it 
with  a  bell  glass.  The  oxygen 
within  the  bell  will  be  con- 
sumed, and  white  clouds  of 
phosphoric  anhydride  be  formed. 
These  will  soon  be  absorbed  by 
the  water,  and  the  gas  remaining 
is  nearly  pure  nitrogen.  Nitro- 
gen may  also  be  obtained  by  boiling  a  solution  of  potassium  nitrite 
mixed  with  thrice  its  volume  of  a  strong  solution  of  ammonium 
chloride:  NH4C1  -f  KN02  =  KC1  +  2  H2O  -f  2~&.  (See  §  722.) 

196.  Physical  properties.    Nitrogen  is  a  colorless,  odor- 
less, tasteless,  permanent  gas. 

197.  Chemical  properties.    Free  nitrogen  is  remarkable 
for   its    chemical   inactivity.     It   is   neither   combustible 
nor  a   supporter  of  combustion.     At  elevated   tempera- 
tures it  combines  with  titanium,  carbon,  oxygen,  and  a 
few  other  elements.     It  also  unites  with  nascent  hydro- 
gen :    thus,  when   iron  rusts  in   moist  air,   a  little  am- 
monia is  frequently  found  absorbed  by  the  ferric  oxide. 

The  organic  compounds  of  nitrogen  are  exceedingly 
prone  to  decomposition.  The  mineral  compounds  are 
often  unstable  and  explosive,  as  is  especially  the  case 
with  those  that  contain  the  radical  nitryl  (NO2).  This 
character  of  instability  renders  many  of  the  nitrogen 
compounds  energetic  chemical  agents. 


128 


CHEMISTRY 


TESTS. — A  gas  which  does  not  give  any  reaction  with  any  known 
chemical  test  may  be  pronounced  nitrogen.  Solid  organic  matters 
containing  nitrogen,  when  heated  with  a  mixture  of  caustic  soda  and 
lime,  yield  ammonia  H3N. 

198.  Uses.  The  use  of  free  nitrogen  in  the  air  appears 
to  be  to  prevent  the  too  rapid  action  that  would  take 
place  in  pure  oxygen. 


AMMONIA,  H3N. 

199.  Ammoniacal  compounds  are  but  sparingly  found 
in  nature,  although  ammonia  is  constantly  produced  in 
the  putrefaction  of  animal  and  vegetable  matters.     The 
reason    for    this   seems    to    be    that    plants  derive    their 
chief  supply    of   nitrogen    from    the    salts    of  ammonia, 
which    are   brought   down  by  the  rain  from  the  atmos- 
phere, and  so  consume  it  as  rapidly  as  it  is  formed. 

200.  Preparation.     The  commercial  source  of  ammonia 
and   its   compounds   is    the    so-called    sal-ammoniac  ,   or 
ammonium  chloride,  NH4C1.     This  is  obtained  in  large 

quantities    in    the    process   of  making 
illuminating  gas  from  coal. 

Exp.  127. — Rub  together  30  grammes  of 
pulverized  sal  ammoniac  and  60  grammes  of 
powdered  quicklime.  The  heat  caused  by  the 
friction  will  be  sufficient  to  evolve  the  gas. 


Exp.  128. — To  collect  the  gas,  pour  this 
mixture  into  a  flask  to  which  a  tube  has  been 
fitted;  then  add  60  cc.  of  water,  and  heat. 
Collect  by  upward  displacement.  (Fig.  60).  It 
may  be  dried  by  passing  it  through  a  bottle 
containing  lumps  of  quicklime. 

2  (NH4C1)  +  CaO  =  CaCl2  +  H2O  + 


FIG.  60. 


Exp.  129.— It   may  also   be   collected   for  purposes   of  experi- 
ment by  gently  heating  aqua  ammonia  and  drying  the  gas. 


AMMONIA. 


129 


201.  Physical  properties,     Ammonia  is  a  colorless,  co- 
ercible gas  of  a  pungent  odor :    sp.  gr.  0,59.     Aqua  am- 
monia  is   a   solution    of  the  gas  in  water,  obtained  by 
passing  a  stream  of  the  gas  through  bottles  containing 
water,  and  kept  cool  by  ice.     One  volume   of  water   at 
15°  C.  absorbs  783  volumes  of  the  gas,  and  increases  in 
volume  one-half:  sp.  gr.  0.85.     This  solution  is  the  aqua 
ammonia  of  commerce.     The  amount  of  the  gas  retained 
in  the  solution  varies  with  the  temperature  and  pressure. 

Exp.  130.— Fill  a  barometer  tube  over  30 
inches  long  with  one  inch  of  concentrated  aqua 
ammonia  and  sufficient  mercury  to  occupy  the 
remaining  space,  and  invert  the  tube  under 
mercury.  On  removing  the  finger  the  Torricel- 
lian vacuum  will  be  formed,  and  the  ammonia 
solution  will  boil  from  the  escape  of  a  large 
quantity  of  the  gas.  (Fig.  Gl).  The  gas  may  be 
re-absorbed  on  depressing  the  tube  in  a  tall 
cylinder  of  mercury,  because  of  the  increased 
pressure.  It  may  then  be  re-expelled  by  pouring 
hot  water  on  the  top  of  the  tube. 

Exp.  131. — To  show  the  rapid  absorption 
of  ammonia  by  water,  Exp.  95  may  be  repeated 
with  dry  ammonia  gas. 

The  gas  may  be  condensed  at  — 40°  C. 
to  a  clear  liquid  which  solidifies  at  —  75° 
C.  It  may  also  be  liquefied  at  10°  C.  by 
a  pressure  of  six  atmospheres.  The  liquid 
evaporates  rapidly  and  absorbs  a  large 
amount  of  heat.  Carre's  freezing  apparatus  utilizes  these 
properties  of  ammonia  in  the  production  of  artificial  ice. 

202.  Chemical    properties.      The    feeble    combustible 
power  of  ammonia  has  already  been  shown  in  Exp.  49. 
Both    the    gas    and    the    solution    have    strong   alkaline 
properties,  which  will   be   considered  in  the  chapter  on 
alkalies. 

Chem.— 9. 


130  CHEMISTRY. 

TESTS. — Free  ammonia  is  detected  (1)  by  its  odor;  (2)  by  its 
action  on  moistened  red  litmus  paper;  (3)  by  giving  white  fumes 
of  NH4C1  when  a  glass  rod  dipped  in  HC1  is  brought  in  contact 
with  it. 

Ammoniacal  salts  yield  free  NH3  when  heated  with  soda-lime 
or  with  KHO.  Traces  of  aqua  ammonia  or  of  ammoniacal  salts 
are  detected  by  forming  a  brownish  precipitate  on  the  addition  of 
"Nessler's  test."* 

203.  Ammonia  derivatives,  Each  of  the  hydrogen 
atoms  in  ammonia  may  be  exchanged  for  a  monad 
radical  (elementary  or  compound),  and  thus  give  rise 
to  new  compounds  which  may  be  considered  as  formed 
on  the  type  of  one  or  more  molecules  of  ammonia. 

(I)  When  a  positive  radical 
takes  the  place  of  the  hydro- 
gen, an  amine  compound  is 
formed.  Thus,  potassamine 
forms  when  dry  ammonia  gas 
is  passed  over  a  clean  pellet 
of  potassium,  gently  heated. 

H3N  +  K  =  KH2N  +  H. 

If  potassamine  is  strongly  heated,  it  becomes  tripotassa- 
mine  :  3KH2N  =  K3N  +  2II3N. 

(II)  When  a  negative  radical  takes  the  place  of  the 
hydrogen,  an  amide  compound  is  formed. 

Exp.  132. —Rub  together  a  gramme  of  iodine  and  16  cc.  of 
aqua  ammonia.  On  standing  for  thirty  minutes,  a  brown  powder, 
usually  called  iodide  of  nitrogen,  is  formed. 

3H3N  +  I4  =  I2HN  +  2(NH4I). 


-This  is  prepared  by  adding  to  a  gramme  of  KI,  dissolved  in  H2O,  enough 
HgCl2  to  re-dissolve  the  precipitate  which  forms.  Four  grammes  of  KHO  are 
then  added,  and  water  enough  to  make  the  volume  of  100  cc.  The  liquid 
is  then  allowed  to  stand  until  it  becomes  clear,  and  the  solution  is  preserved  in 
tightly  corked  bottles. 

4HgK2I4  +  6KHO   f  2(NH3H2O)  =  Hg4N2I2,  2H2O  +  14KI  +  6H2O. 


NITROGEN  AND   OXYGEN  COMPOUNDS.         131 

It  may  also  be  termed  di-iodamide.  Collect  the  powder  on  a  filter, 
divide  it  into  four  or  five  portions,  and  suffer  them  to  dry  in  a 
quiet  place.  When  dry,  it  explodes  if  touched  even  by  a  feather. 
A.  chloride  of  nitrogen,  C13N,  C12HN,  or  a  trichloramide  may 
be  formed  by  exposing  sal-ammoniac  to  the  action  of  chlorine  gas. 
It  is  so  violently  explosive  that  none  but  expert  chemists  should 
attempt  to  prepare  it. 

(Ill)  These  derivative  compounds  are  sometimes  called 
a?nides,  imides,  and  nitriles,  as  if  formed  from  the  radicals, 
NH2  (amidogen),  NH  (imidogen),  and  trivalent  nitrogen. 

204.  There  are  also  derivatives  containing  both   posi- 
tive and  negative  radicals,  which  are  called  alkalamides. 
In    some    ammoniacal    compounds  the   nitrogen  appears 
to  be  pentavalent,  as  sal-ammoniac,  NH4C1.     If  ammonia 
be   added   in   excess   to   mercuric  chloride,  a  white  pre- 
cipitate forms   of  the   formula   NF2H'4Hg"2Cl'2    (dimer- 
curic  dichloramide).     If  ammonia   be   added   to  freshly 
precipitated  mercurous  chloride,  black  mercurous  chlor- 
amide  (N^I^Hg^Cl')  forms.     Both  of  these  are  alkal- 
amide  compounds. 

COMPOUNDS  OF  NITROGEN  AND  OXYGEN. 

205.  There  are  five  oxides  of  nitrogen,  viz : 

Protoxide,  or  nitrous  oxide,  N2O. 

Dioxide,  or  nitric  oxide,  N2O2  ;    nitrosyl  (NO)'. 

Teroxide,  or  nitrous  anhydride,  N2O3. 

Tetroxide,  or  nitric  peroxide,  N2O4  ;  nitryl  (NO2)'. 

Pentoxide,  or  nitric  anhydride,  N2O5. 

Three  of  these  oxides  unite  with  water  to  form  acids: 

N2O    -f  H2O  =  H2O,  N2O     or  2  (HNO),  hyponitrous  acid. 
N2O3  -f  H2O  =  H2O,  N2O3  or  2  (HNO2),  nitrous  acid. 
N2O5  +H2O  =  H2O,  N2O5  or  2(HNO3),  nitric  acid. 

The  dioxide  and  the  trioxide  have  no  corresponding  acids.  All 
of  these  oxides  are  obtained  from  nitric  acid. 


132 


CHEMISTRY. 


206.  The  nitrates    are    formed    by    the    oxidation    of 
nitrogenous   organic   matters   in   the   presence  of  strong 
bases.     Potassium   nitrate,  or  saltpeter,  occurs  native  in 
India,  and  is  also  largely  manufactured  by  the  decompo- 
sition of  other  crude  nitrates.     Sodium   nitrate,  or  Chili 
saltpeter,  occurs  in  large  beds  in  South  America.    Rain- 
water also  contains  traces  of  nitrates,  which  may  come 
cither  from  the  oxidation  of  ammonia  or  from  the  action 
of  atmospheric  electricity. 

207.  Nitric  acid  is  a  monobasic  acid,  having  the  for- 
mula IINO3  ;  but  we  shall  frequently  find  it  convenient 
to   use   the    binary  formula  H2O,  N2O5,  which  contains 
two   molecules.     It   is   obtained   by   distilling   a   nitrate 
with  strong  sulphuric  acid. 

Exp.    133.  —  Heat 

equal  weights  of  salt- 
peter and  strong  sul- 
phuric acid,  and  collect 
the  distillate  in  a  re- 
ceiver kept  cool  by 
water.  Red  fumes  ap- 
pear at  the  beginning 
of  the  process,  but  after- 
ward a  nearly  colorless 
acid  collects  in  the  re- 
ceiver. (Fig.  63). 


FIG.  63. 
KN03  -f  H2S04  =  KHS04  -f 

When  the  distillation  has  ceased,  and  the  retort  has  somewhat 
cooled,  warm  water  may  be  added  and  the  solution  poured  out. 
This  yields,  on  evaporation,  crystals  of  acid  potassium  sulphate. 
When  half  the  quantity  of  sulphuric  acid  is  used,  the  same  reac- 
tion takes  place  in  the  first  stages,  but  afterward  the  acid  sulphate 
acts  upon  the  saltpeter  remaining  to  form  normal  potassium  sul- 
phate: KHSO4  -f  KNO3  =  K2SO4  -f  HNT>3.  This,  however,  is  not 
advantageous,  because  the  heat  required  is  so  great  as  to  decompose 
a  part  of  the  nitric  acid,  and  because  the  normal  sulphate  is  less 
easily  removed  from  the  retort. 


NITRIC  ACID.  133 

208.  Physical  properties.     Pure  nitric  acid  is  a  color- 
less, volatile  liquid  of  the  specific  gravity  1.52.     It  solid- 
ifies at   —  55°   0.,    and    boils    at  86°  C.     Nitric   acid   is 
usually  more   or   less   colored,  owing   to   the  absorption 
of  the  lower  oxides  of  nitrogen,  which  are  the  products 
of  its    own    partial    decomposition.     Red    fuming    nitric 
acid  is  the  strong  acid  containing  a  considerable   quan- 
tity of  pernitric  oxide.     The  ordinary  aqua  fort  is  contains 
from  30  to  GO  per  cent  of  nitric  acid. 

209.  Chemical    properties.     Nitric    acid   is    easily   de- 
composed   into    water,    oxygen,    and    a    lower    oxide    of 
nitrogen.     For   this    reason    it   is    a    powerful    oxidizing 
agent. 

Exp.  134.—  Pour  a  little  of  the 
strongest  nitric  acid  upon  warm, 
powdered  charcoal:  the  latter  takes 
fire  at  once. 

Exp.  135.  —  Drop  a  small  pellet 
of  phosphorus  into  the  strongest 
nitric  acid  (placed  at  some  distance 
from  the  operator,  to  avoid  danger). 

It  oxidizes,  and  frequently  with  such  FIG.  64. 

violence  as  to  burst  into  flame.     (Fig.  64). 

In  like  manner,  sulphur  and  iodine,  when  heated  with 
nitric  acid,  are  converted  to  sulphuric  and  iodic  acids. 
When  nitric  acid  is  poured  upon  the  ordinary  metals, 
it  oxidizes  them  and  is  itself  reduced  to  one  of  the 
lower  oxides  of  nitrogen.  The  usual  reactions  may  be 
illustrated  by  the  following  experiments. 

Tfo-p.  136.  —  Add  nitric  acid  to  tin  foil.  The  latter  is  converted 
into  white  metastannic  acid. 


10(H20,  N205)  +  5Sn  =Sn5010,  10H2O 
The  red  fumes  are  nitric  peroxide.  If  the  white  tin  powder  be 
mixed  with  slaked  lime  and  gently  warmed,  ammonia  will  be  given 
off,  showing  that  a  portion  of  the  acid  has  been  converted  into 
H3N. 


134  CHEMISTRY. 

Exp.  137.  —  Add  strong  nitric  acid  to  copper  clippings.  A 
portion  of  the  acid  will  be  reduced  to  nitric  oxide,  and  cupric 
oxide  is  formed:  another  portion  unites  with  the  cupric  oxide  to 
form  blue  cupric  nitrate. 


4(H2O,  N2O5)  +  3Cu  =  3(CuO,  N2O5)  +  4H2O 

This  is  the  usual  reaction  with  the  metals.  The  nitric 
oxide  is  itself  colorless,  but  is  converted  by  contact  with 
the  air  into  red  nitric  peroxide.  (See  §  392). 

Nitric  acid  acts  energetically  upon  organic  matters. 
(1)  It  oxidizes  them:  thus,  indigo  is  converted  to  isatin, 
and  is  thereby  bleached.  Starch  and  sugar  are  converted 
to  oxalic  acid.  (2)  It  forms  substitution  products  through 
the  displacement  of  one  or  more  atoms  of  hydrogen  in 
the  original  compound  by  the  radical  nitryl  (XO2)'. 
Thus,  benzole,  C6IIG,  treated  with  strong  nitric  acid, 
becomes  nitro-benzole,  C6II5(XO2);  phenol,  or  carbolic 
acid,  C6II6O,  yields  tri-nitro-phenol,  or  picric  acid, 
C6II3(NO2)3O.  This  latter  substance  is  a  permanent 
yellow  dye.  Nitric  acid  stains  the  skin  and  many  other 
organic  substances  yellow,  probably  from  the  formation 
of  picric  acid. 

Exp.  138.  —  Dip  a  skein  of  white  silk  thread  into  dilute  nitric 
acid  for  a  few  minutes;  then  wash  thoroughly  with  water.  It  will 
be  colored  permanently  yellow. 

The  TESTS  for  free  nitric  acid  are:  (1)  its  bleaching  power  upon 
indigo;  (2)  the  red  fumes  which  it  evolves  when  added  to  copper 
filings.  The  normal  nitrates  are  all  soluble  in  water.  Nitric  acid 
in  combination  is  detected  by  warming  the  nitrates  with  strong 
sulphuric  acid,  and  applying  either  of  the  above  tests.  (3)  By 
adding  to  the  mixture,  when  cold,  a  crystal  of  ferrous  sulphate. 
A  brownish  color  indicates  the  presence  of  nitric  oxide.  (Exp.  142). 

210.  Nitric  anhydride,  N2O5,  may  be  obtained  by  very 
gently  heating  silver  nitrate  in  a  slow  current  of  dry 
chlorine  gas.  It  is  a  crystalline,  unstable  solid,  which 
readily  unites  with  water  to  form  nitric  acid. 


NITROUS  OXIDE.  135 

211.  The  uses  of  nitric  acid  as  an  energetic  oxidizing 
agent    have    already    been    indicated.      Its    substitution 
products,  gun  cotton  and  nitro-glycerme,  are  very  pow- 
erful explosive  compounds.     Nitro-benzole  is  used  as  an 
artificial  perfume,  and  as  a  material  from  which  aniline 
can  be  made.     Engravers   employ  the   acid   for   etching 
designs  upon  copper  and  steel.     It  attacks  all  the  metals 
except  gold  and  the  metals  of  the  platinum  group. 

212.  Aqua   regia   is  a  mixture   of  one  part  of  nitric 
acid   with   three   parts   of  hydrochloric    acid.     The    two 
liquids   react    upon   each  other  and  liberate  chloronitric 
gas  and  free  chlorine. 

H20,  N205  +  6HC1  =  2N$C12  +  4H2O  +  (jT2. 

A  small  quantity  of  chloronitrous  gas,  NOC1,  is  formed  at 
the  same  time.  The  presence  of  the  free  chlorine  renders 
aqua  regia  a  solvent  for  gold  and  platinum.  It  should 
be  prepared  as  wanted  for  use. 

213.  Nitrous  oxide,  N2O,  is  pre- 
pared by  gently  heating  ammonium 
nitrate.    The  salt  readily  melts  and 
soon  appears  to  boil,  and  is  entirely 
decomposed  into  \vater  and  nitrous 
oxide. 


NH4,N08   heated  =  2  H2O-f 

214.  Physical  properties.  Nitrous 
oxide  is  a  colorless,  coercible  gas, 

having  a  faint  odor  and  a  sweetish  taste:  sp.  gr.  1.53. 
It  liquefies  at  7°  C.,  under  a  pressure  of  40  atmospheres, 
and  solidifies  at  —  100°  C.  The  lowest  temperature  yet 
attained,  --140°  C.,  was  produced  by  evaporating  in 
vacuo  a  mixture  of  liquid  nitrous  oxide  and  carbon  di- 
sulphide.  The  gas  may  be  collected  by  displacement 
or  over  warm  water.  Water  at  15°  C.  absorbs  three- 
fourths  of  its  volume  of  the  gas. 


136  CHEMISTRY. 

215.  The  chemical  properties  of  nitrous  oxide  resemble 
those   of  oxygen  ;    but  it  does  not  form  red  fumes  with 
nitric  oxide. 

Exp.  139.  —  Into  jars  of  the  gas,  plunge  (1)  an  ignited  splinter 
of  wood  —  it  will  burst  into  flame:  (2)  sulphur  or  phosphorus  heated 
in  a  deflagrating  spoon  —  the  combustion  will  be  very  brilliant. 

216.  The  physiological  properties  of  the  gas  have  given 
it  the  name  of  "  laughing  gas,"  because,  when  breathed 
in    moderate    quantity,    it    produces    stimulating    effects. 
Breathed  in  large  quantity,  it  produces  temporary  stupor, 
and  is  used  as  an  anaesthetic  in  dental  surgery.* 

The  hyponitrite  of  sodium  (NaNO)  is  formed  by  adding  sodium 
amalgam  to  a  solution  of  sodium  nitrate.  If  the  excess  of  the  alkali 
be  neutralized  by  acetic  acid,  the  hyponitrous  acid  is  liberated,  but 
immediately  decomposes  to  water  and  nitrous  oxide: 


217,  Nitric  oxide,  N2O2  or  NO,  is  usually  prepared  by 
treating   copper   clippings  or   mercury    with    moderately 
dilute  nitric  acid.     (Exp.  137.)     The  gas  may  be  collected 
over  water,  which  absorbs  the  red  fumes  formed  by  the 
union  of  the  NO  with  the  air  in  the  generating  flask. 

218,  Physical  properties.     Nitric  oxide  is  a  colorless, 
gas   (sp.  gr.  1.04),  very  slightly  soluble  in  water,  which 
liquefies  under  a  pressure  of  146  atmospheres. 

219,  Chemical   properties.     Nitric   oxide   may   be   con- 
sidered as  the  free  state  of  the  monatomic  radical  nitro- 
syl  (NO).     It  is  one  of  the  most  stable  of  the  nitrogen 
oxides.     Ordinary  combustibles   do   not  burn   in   it;   but 
phosphorous  or  carbon,  when  burning  briskly,  is  able  to 
decompose  the  gas  and  combine  with  its  oxygen. 

Exp.  140.  —  Into  a  jar  of  the  gas  plunge  a  piece  of  dried  phos- 
phorus just  ignited:  it  will  be  extinguished.  Again  introduce  the 
phosphorus  when  in  full  combustion:  it  will  burn  as  in  oxygen. 

-'•CAUTION.—  If  the  gas  is  to  be  used  for  inhalation,  the  ammonium  nitrate 
should  be  free  from  sal-ammoniac,  as,  otherwise,  it  will  be  mixed  with  chlorine. 


NITRIC  OXIDE.  137 

The  special  characteristic  of  nitric  oxide  is  its  strong 
attraction  for  free  oxygen.  It  unites  directly  with  it, 
producing  deep  red  fumes  which  are  chiefly  nitric  per- 
oxide, N2O4,  but  mixe(i  with  nitrous  anhydride,  N2O3. 

Exp.  141. — Fill  a  small  jar 
with  blue  litmus  water,  and  de- 
cant into  it  a  pint  of  oxygen. 
Now  add  a  pint  of  nitric  oxide. 
Red  fumes  are  formed  which 
are  soon  absorbed  by  the  water. 
Now  add  another  pint  of  nitric 
oxide.  If  both  the  oxygen  and 
the  nitric  oxide  are  pure,  the 
gases  will  be  completely  ab- 
sorbed by  the  water,  showing 

that   nitric  peroxide  is   formed  FIG> 

by  the   union   of  two   volumes 
of  nitric  oxide  with  one  of  oxygen.     The  litmus  becomes  red. 

Owing  to  this  ready  combination  with  oxygen,  the 
actual  taste,  odor,  and  respirability  of  nitric  oxide  have 
not  been  ascertained. 

Nitric  oxide  is  readily  absorbed  by  solutions  of  the 
ferrous  salts,  forming  compounds  such  as  2FeSO4,NO. 

Exp.  142. — Shake  a  little  ferrous  sulphate  in  a  jar  of  the  gas: 
a  brown  solution  will  be  formed,  which,  on  exposure  to  the  air  or 
on  warming,  soon  becomes  colorless. 

220.  Nitrous    anhydride,    N2O3,   is   best   prepared   by 
gently    heating    nitric    acid    with    an    equal    weight    of 
arsenious  acid,  and  collecting  the  distillate  in  a  U  tube 
surrounded  by  a  freezing  mixture. 

H20,  N205  +  As203  =  II20,  As205  +  K£)8. 

221.  Physical  properties.    The  nitrous  anhydride  thus 
obtained    is   a   blue    liquid,    easily   decomposed    by   heat, 
and  forming  with  water  at  0°  C.  a  blue  liquid  which  is 
nitrous  acid,  II2O,  N2O3  or  HNO2. 


138  CHEMISTRY. 

222.  Nitrous  acid  is  stable  only  at  low  temperatures 
or  in  very  dilute  solutions.  When  heated,  it  decomposes 
into  nitric  oxide,  which  escapes  with  effervescence,  and 
into  nitric  acid  and  water,  which  remain  in  the  solution. 

The  alkaline  nitrites  are  produced  by  heating  the 
alkaline  nitrates  to  redness.  Oxygen  is  given  off;  a 
mixture  of  free  alkali  and  nitrite  remains. 

Exp.  143.— Heat  potassium  nitrate  in  a  crucible  until  a  portion, 
removed  on  the  end  of  an  iron  rod,  gives 
a  strong  alkaline  reaction.  Then  pour  the 
fused  mass  on  a  dry  stone,  and,  when  cooled, 
preserve  the  potassium  nitrite  in  stoppered 
bottles. 

Nitrous  anhydride   is    disengaged 
when  a  nitrite  is  treated  with  a  dilute 
acid.     It  is,  however,  almost  imme- 
diately decomposed  into  nitric  oxide 
FIG.  67.  fn,  .,1^1 

and  nitric  acid.     The  acidulated  so- 
lutions of  the  nitrites  act : 

(T)  As  reducing  agents. 

Exp.  144. — To  a  solution  of  potassium  permanganate,  add  a 
few  clrops  of  sulphuric  acid  and  then  a  solution  of  potassium  nitrite. 
The  red  color  disappears:  MnO,  SO3  is  formed. 

(II)  As  oxidizing  agents. 

Exp.  145. — To  a  dilute  indigo  solution,  add  a  solution  of  po- 
tassium nitrite  and  then  a  few  drops  of  sulphuric  acid.  The  indigo 
is  changed  to  isatin  and  bleached. 

Exp.  146. — To  a  solution  of  potassium  iodide,  add  the  nitrite 
and  acidulate.  The  potassium  is  oxidized  and  the  iodine  set  free. 
The  iodine  may  be  detected  by  starch  paste,  or  dissolved  out  of  the 
aqueous  solution  by  carbonic  disulphide. 

TESTS. — The  above  reactions  are  also  tests  for  nitrous  acid.  The 
nitrites  are  distinguished  from  the  nitrates  by  giving,  with  ferrous 
salts,  a  brown  discoloration  without  the  addition  of  an  acid. 


NITRIC  PEROXIDE. 


139 


223.  When  ammonia  is  burned  in  the  air  it  is  decom- 
posed, and  both  of  its  constituents  unite  with  oxygen  — 
the  hydrogen  to  form  water,  the  nitrogen  to  form  nitrous 
anhydride  or  some  other  oxide  of  nitrogen. 

Exp.  147.s — Shake  copper  filings,  with  a  little  strong  aqua 
ammonia,  in  a  large  flask.  White  fumes  will  be  produced,  the 
liquid  will  become  blue,  and  will  be  found  to  contain  oxide  of 
copper  and  nitrite  of  ammonia. 


Exp.  148.— Suspend  a  highly  heated 
coil  of  thin  platinum  wire  in  a  flask  con- 
taining a  little  strong  aqua  ammonia. 
Thick,  white  clouds  of  ammonium  nitrite 
are  formed,  and  sometimes  red  vapors  of 
nitrous  anhydride.  If  a  tube  delivering 
oxygen  be  passed  into  the  flask,  the  action 
will  be  more  energetic.  The  spiral  will 
glow  for  some  time,  the  red  fumes  will 
bo  more  abundant,  and  little  explosions 
rapidly  succeed  one  another. 


FIG.  68. 


224,  Nitric    peroxide,    N204    or 

NO2,  has  already  been   mentioned 

as  forming  the  greater  part  of  the  red  fumes  which  are 

produced  by  the  action  of  oxygen  upon  nitric  oxide. 

225,  Physical  properties.     It  is  possible   to   condense 
these    fumes    into    a    crystalline    solid    which    melts    at 
— 9°  C.,  or  to  a  volatile,  almost  colorless   liquid   whose 
color  changes,  as  the  temperature  rises,  from  a  greenish 
yellow   to   yellow,    and   then   to  orange.     At  22°  C.   it 
boils  and  forms  red  vapors,  which  may  become  so  dark 
as  to  be  almost  opaque.     These  vapors  are  irrespirable, 
and  have  a  pungent,  suffocating  odor. 

226,  Chemical  properties.    Although  ordinary  combus- 
tibles are  extinguished  by  nitric  peroxide,  it   is   an   en- 
ergetic oxidizing  agent.    Its  use  in  converting  sulphurous 
to  sulphuric  acid   has   already  been  mentioned.     In  the 


140  CHEMISTRY. 

presence  of  water  it  is  decomposed  into  nitrous  and 
nitric  acids,  with  the  formation  of  a  liquid  whose  color 
varies  from  green  to  blue,  according  to  the  proportion 
of  nitrous  acid  and  unaltered  nitric  peroxide  present. 
The  same  coloration  is  frequently  observed  when  silver, 
mercury,  or  lead  is  dissolved  in  nitric  acid,  sometimes 
leading  the  novice  to  suspect  the  presence  of  copper. 

Nitric  peroxide  acts  as  the  free  molecule  of  the  mon- 
atomic  radical  nitryl,  NO2,  which  is  capable  of  replacing 
hydrogen  in  many  organic  compounds. 

PHOSPHORUS. 

227.  Phosphorus  is  never  found  uncombined  in  nature, 
but  is  very  widely  and  abundantly  diffused  in  the  form 
of  phosphates.     Calcium  phosphate,  the   chief  source  of 
this  element,  is  found  in  guano,  coprolites,  and  in  apatite. 
It  is  also  found  in  small  quantities   in   all    arable    soils, 
whence    it    is    taken    up   by  plants   and   accumulated  in 
their   seeds.     The   animals  which  feed  upon  these  seeds 
assimilate  it,  and  hence  it  forms  a  part  of  almost  every 
solid  and   liquid   in   the  bodies  of  animals.     The  bones 
of  oxen  contain  nearly  58  per  cent  of  calcium  phosphate 
and  2  per  cent  of  magnesium  phosphate.     When  bones 
are  burnt  they  leave  a  white  and  friable  ash,  which    is 
impure  tri-calcium  phosphate,  3CaO,  P2O5. 

228,  Preparation.     Phosphorus  and  its  compounds  are 
obtained  from  this  "  bone  ash." 

(1)  The  ground   bones    are  digested    for  some  hours  with  two- 
thirds  their  weight  of  strong   sulphuric   acid   and    six    times   their 
weight    of   water.     An    insoluble   calcium    sulphate   ancj.   a    soluble 
monocalcic  phosphate,  or  "superphosphate  of  lime,:'  are  formed. 

3  CaO,  P205  +  2  (H20,  SO3)  =  2  (CaOSO3)  +  CaO,  2  H2O,  P2O5. 

(2)  The  calcium  sulphate  is  removed  by  filtration.    The  solution 
is  then  evaporated  to  a  syrup,  and  is  then  mixed  with   one-fourth 


PHOSPHORUS.  141 

of  its  weight  of  charcoal,  and  heated   to   redness.     The  monocalcic 
phosphate  is  converted  into  calcium  meta-phosphate,  CaO,  P2O5. 

CaO,  2  H20,  P205  heated  =  CaO,  P2O5  +  2  H"2O. 

(3)  On  distilling  this  mixture  of 
charcoal  and  calcium  rnetaphosphate 
in  a  retort,  phosphorus   is   set   free, 
passes   over   in    vapor,  and  may  be 
condensed  under  water.    The  calcium 
retains    enough    of  the    acid  to    re- 
convert  it   into  tricalcic  phosphate. 

3(CaO,P2O5)  -f  10 C  = 

3 CaO,  P20.  +  10CO  +  P;.  FIG.  eg. 

(4)  The  crude  phosphorus  thus  prepared   is   purified  by  melting 
it   under  water    containing   a   little   chromic   acid.     It  is  then  run 
into   a   horizontal   tube   surrounded   by   cold   water,  by  which  it  is 
chilled,  and  is  then  drawn  out  in  solid  sticks. 

229.  Physical  properties.     Pure  phosphorus,  when  first 
made,  is  an   almost  colorless,  translucent    solid :    sp.  gr. 
1.82.     It  melts  at  44°  C.,  and  boils  in  closed  vessels  at 
290°  C.     The    vapor    density   at    500°,    referred    to   the 
hydrogen  unit,  is  62.1,  which  is  double  its  atomic  weight; 
from  which  it  appears  that  the  atom  of  phosphorus  oc- 
cupies  only  half  the  volume  of  the  hydrogen  atom,  or 
that  the  molecule  of  phosphorus  contains  four  atoms. 

Phosphorus  is  somewhat  soluble  in  turpentine  and  in 
essential  and  fixed  oils.  It  is  readily  dissolved  by  carbonic 
disulphide.  If  this  solution  be  evaporated  in  an  atmos- 
phere of  carbonic  anhydride,  the  phosphorus  may  be 
obtained  in  dodecahedral  crystals. 

230.  Chemical  properties.     Phosphorus  exposed  to  the 
air  at  ordinary  temperatures  undergoes  a  slow  combus- 
tion,  and   is  feebly  luminous   in    the    dark.     Hence    its 
name,   which   means   the    light-bearer    (c£<x»c,  (pepa)).     It 
is  extremely  inflammable,  taking  fire  in  the  air  a  little 
above  its  melting  point.     (Compare  Exp.  48).     On  this 


142  CHEMISTRY. 

account  it  is  kept  under  water,  and  should  be   handled 
with  great  caution. 

Phosphorus  combines  readily  with  many  of  the  ele- 
ments. (Exps.  10,  74,  88).  Its  compounds  with  the 
metals  are  called  phosphides  or  phosphurets.  Owing  to 
the  strong  affinity  of  phosphorus  for  oxygen,  it  is  an 
energetic  reducing  agent,  and  is  capable  of  precipitating 
copper,  lead,  and  some  other  metals  from  solutions  of 
their  salts. 

Exp.  149. — Place  a  pellet  of  phosphorus  in  a  solution  of  silver 
nitrate.  In  a  few  days  it  will  be  covered  with  metallic  silver. 

231.  Phosphorus  is   capable  of  assuming  several  allo- 
tropic  states,  the  most  remarkable   of  which  is  the  red, 
or  amorphous,  phosphorus.     This   may  be   prepared    by 
heating  ordinary  phosphorus  in  an  atmosphere   of  car- 
bonic anhydride,  at  a  temperature  of  230°  to  235°  C.,  for 
thirty  hours.     The  two  modifications  differ  so  much  that 
we  should  suppose  them  to  be  different  elements   if  we 
could    not    convert    one    into  the   other.     The  red  phos- 
phorus   has   a    specific   gravity   of  2.14,   is   insoluble    in 
carbon  disulphide,  does    not    inflame   by  friction,  is  un- 
altered in  the  air,  and   is   not   poisonous.     If  heated  to 
260°  C.,  it   is   converted    into   ordinary  phosphorus  and 
bursts  into  a  flame. 

Ordinary  phosphorus  is  very  poisonous.  Cases  have 
occurred  in  which  children  have  been  poisoned  by  suck- 
ing the  phosphorus  combination  on  the  tips  of  matches. 
Its  vapor  sometimes  causes  a  necrosis  of  the  jaw-bone. 
The  best  antidote  is  calcined  magnesia. 

232.  Uses  of  phosphorus.    "  Lucifer  matches  "  are  made 
by  tipping  small  wooden  sticks  with  sulphur  or  paraffme, 
to  convey  the  flame,  and,  afterward,  with  a  composition 
containing  ordinary  phosphorus,  glue,  and  an  oxidizing 
substance   like    saltpeter   or   potassium   chlorate.     These 
matches  take  fire  when  rubbed  on  any  rough  surface. 


PHOSPHURETTED  HYDROGEN.  143 

"  Safety  matches  "  are  tipped  with  a  mixture  of  anti- 
monous  sulphide  and  potassium  chlorate.  These  do  not 
readily  take  fire  by  friction,  but  inflame  when  they  are 
rubbed  on  a  surface  containing  amorphous  phosphorus, 
manganese  dioxide,  and  fine  sand. 

Various  attempts  have  been  made  to  manufacture  matches  with- 
out phosphorus.  Good  matches  have  been  made  with  a  composition 
of  potassium  chlorate  and  lead  hyposulphite. 

A  very  common  rat  poison  is  made  from  ordinary  phosphorus 
mixed  with  flour  paste. 

233.  Tests,     Free,    ordinary    phosphorus   may   be   de- 
tected   by   its    luminosity   in    the    dark ;    phosphorus    in 
combination,  by  heating  the  dry  powder  which  contains 
it  in  a  thin  glass  tube  with  a  small   bit   of  magnesium 
or  sodium.     On   breaking  the  tube  and   adding   water, 
the  odor  of  hydrogen  phosphide  will  be  perceived,  and 
frequently,    also,   its    flame.     Any    one    of  its    allotropic 
forms   may  be   detected   by   oxidizing   it  to   phosphoric 
acid,  and  applying  the  test  for  that  body. 

234.  Compounds  of  phosphorus  and  hydrogen.     Three 
of  these  compounds  are  known :    (1)    a  solid  phosphide, 
HP2(?);    (2)   a  spontaneously  inflammable   liquid   phos- 
phide, H2P;  and  (3)  gaseous  phosphide,  H3P,  generally 
called  phosphuretted  hydrogen. 

235.  Phosphuretted   hydrogen   is  usually  obtained  by 
heating  phosphorus  in  a  strong  alkaline  solution. 

Exp.  150. — Place  in  a  small  flask  a  few  slices  of  phosphorus, 
and  fill  the  flask  with  a  strong  solution  of  caustic  potash.  The 
evolution  tube  should  dip  under  warm  water.  On  gently  heating 
the  flask,  bubbles  of  the  gas  mixed  with  free  hydrogen  escape  into 
the  air,  and  spontaneously  inflame,  with  the  production  of  beautiful 
white  rings  of  phosphoric  anhydride.  (Fig.  70). 


144 


CHEMISTRY. 


FIG.  70. 


236,   Physical  properties.     Phosphuretted  hydrogen  is 

n  colorless,  coercible 
gas:  sp.  gr.  1.19.  It 
has  an  offensive  odor, 
being  the  same  as  that 
evolved  by  putrid  fish. 

237.  Chemical  prop- 
erties. The  gas  is  not 
spontaneously  inflam- 
mable. This  property 
is  given  it  by  the  pres- 
ence of  a  small  quan- 
tity of  the  liquid  phos- 
phide of  hydrogen,  and  is  lost  when  the  gas  is  passed 
through  a  freezing  mixture,  or  by  admixture  with  the 
oil  of  turpentine.  It  is  a  very  poisonous  gas. 

When  the  gas  is  passed  into  solutions  of  copper,  a  black  pre- 
cipitate of  copper  phosphide  is  formed.  This  phosphide,  heated  in 
a  solution  of  potassium  cyanide,  evolves  self-lighting  phosphuretted 
hydrogen. 

TESTS. — Its  odor  is  very  characteristic.  Salts  of  silver  and  gold 
are  reduced  to  the  metallic  state  by  this  gas. 

238.  The  terchloride,  PC13,  forms  when  phosphorus  is 
burned  in  chlorine;  or,  if  the  chlorine  be  in  excess,  the 
pentachloride,  PC15.     Both    are    decomposed    by   waiter, 
the  latter  forming  an  oxychloride,  POC13.     Phosphorus 
also  combines  with  bromine,  iodine,  and  sulphur.     These 
compounds  are  of  great  importance  in  organic  chemistry 
in  forming  "substitution  compounds." 

239.  The   oxygen   compounds   of  phosphorus.     Besides 
a    suboxide    of  phosphorus,   P4O,   which    is    imperfectly 
known,    two   anhydrides   of  phosphorus    have   been    ob- 
tained as  bulky,  white,  amorphous  powders,  by  burning 
phosphorus  in  dry  air.     If  the  combustion  is  very  slow, 


HYPOPHOSPHITES.  145 

the  greater  part  of  the  product  is  phosphorous  anhydride, 
P2O3  :  if  the  combustion  is  very  rapid,  the  product  is 
almost  pure  phosphoric  anhydride, 
P2O5.  Both  of  these  anhydrides 
may  be  made  to  combine  with  three 
molecules  of  water  to  form : 

3H2O,  P2O3  or  H3PO3  ==  phosphor- 
ous acid,  FIG.  71. 
3H2O,  P2O5  or  H3PO4  =  phosphoric  acid. 

In  the  case  of  the  phosphoric  anhydride,  it  first  becomes 
Metaphosphoric  acid,  H2O,  P2O5  or  H,  PO3, 

which  is  converted,  upon  boiling  with  water,  into 
Pyrophosphoric  acid,  2H2O,  P2O5  or  H4P2O7, 

and  finally  to  the 

Orthophosphoric  acid,  3H20,  P205  or  H3PO4. 

Hypophosphorous  acid,  H,  PH2O2,  for  which  no  corre- 
sponding anhydride  is  known,  is  another  acid.  The  basic- 
ity of  these  acids  varies  from  one  to  four,  and  is  ex- 
pressed by  the  hydrogen  at  the  left  of  their  formula). 

240.  The  alkaline  hypophosphites  are  formed  by  boiling 
phosphorus   in    alkaline  solutions,  as  in  Exp.   150.     The 
aqueous   solution    of  hypophosphorous   acid    is   obtained 
by  decomposing   barium    hypophosphite   with   sulphuric 
acid. 

The  acid  and  the  alkaline  hypophosphites  are  ener- 
getic reducing  agents.  They  form,  with  silver  nitrate, 
a  white  precipitate  which  quickly  becomes  black,  me- 
tallic silver.  When  the  dry  salts  are  heated,  they  are 
converted  into  phosphates,  and  evolve  phosphuretted 
hydrogen. 

241.  An  impure   phosphorous   acid  is  obtained  by  ex- 
posing  sticks   of  phosphorus  to  the  action  of  moist  air. 
The  solution  readily  absorbs  oxygen,  and  is  changed  to 

Chem.— 10. 


146  CHEMISTRY. 

phosphoric  acid.  It  reduces  silver  nitrate  like  the  hy- 
pophosphites,  but  less  energetically. 

242.  Orthophosphoric  acid  is  prepared  by  oxidizing 
phosphorus  with  nitric  acid. 

5 (H20,  N205)  +  4H20  +  P6  =  3(3II20,  P2O5)  +  10$O. 

This  solution  evaporated  at  a  gentle  heat  forms  a  syrupy 
liquid,  from  which,  by  evaporating  in  vacuo,  hard,  trans- 
parent crystals  may  be  obtained,  called  orthophosphoric 
acid.  The  formula  is  3H2O,  P2O5  or  H3PO4.  This  is 
the  ordinary  phosphoric  acid,  and  is  tribasic. 

If  the  solution  of  orthophosphoric  acid  be  heated  to  215°  C., 
ono  equivalent  of  water  is  expelled  and  pyro-phosphoric  acid  is 
formed,  which  has  the  formula,  2II2O,  P2O5  or  H4P2O7,  and  is 
tctrabasic. 

If  the  solution  is  further  evaporated  in  a  platinum  vessel  until 
white  fumes  begin  to  be  given  off,  a  transparent,  glassy  mass  is 
obtained,  which  is  the  glacial  phosphoric  acid  of  commerce,  or 
mcta-phosphonc  acid.  Its  formula  is  H2O,  P2O5  or  HPO3,  and  it 
is  monobasic.  Metaphosphoric  acid  will  coagulate  the  albumen 
found  in  the  white  of  egg,  and  will  give  a  white,  gelatinous  pre- 
cipitate of  AgPO3  when  it  is  added  to  silver  nitrate. 

The  other  phosphoric  acids  do  not  coagulate  albumen,  nor  do 
they  precipitate  silver  nitrate.  If,  however,  a  few  drops  of  soda 
be  added  to  their  solutions,  the  pyrophosphate  which  is  formed 
will  precipitate  as  white  pyrophosphate  of  silver,  Ag4P2O7;  the 
orthophosphate,  as  yellow  orthophosphate  of  silver,  Ag3PO4. 

Metaphosphoric  acid  forms  but  one  class  of  salts; 
but  both  the  ortho-  and  pyro-phosphoric  acids  form  a 
great  variety  of  salts,  inasmuch  as  their  hydrogen  may 
be  replaced  by  one  or  more  metals,  in  accordance  with 
their  atomicity,  —  a  monad  metal  replacing  one  hydrogen 
atom;  a  dyad,  two,  etc. 

Exp.  151. — Take  the  solution  of  superphosphate  of  lime,  pre- 
pared by  treating  bone  ash  with  sulphuric  acid,  and  add  sodium 
carbonate  until  the  liquid  is  faintly  alkaline.  Filter  off  the  calcium 
carbonate  which  forms,  and  evaporate  the  solution  till  a  drop  of  it 


SODIUM  PHOSPHATES.  147 

placed  on  a  watch  glass  readily  crystallizes.     On  cooling  the  solu- 
tion, crystals  of  di-sodium  phosphate  will  form:  Na2HPO4, 12H2O. 

Exp.  152. — Mix  a  portion  of  the  preceding  solution  with  caustic 
soda,  and  evaporate  as  before.  The  crystals  formed  are  tri-sodium 
phosphate:  Na3PO4, 12H2O. 

Exp.  153. — Mix  another  portion  with  orthophosphoric  acid 
until  it  no  longer  precipitates  calcium  chloride,  and  then  evaporate. 
On  evaporation,  crystals  of  monosodium  phosphate,  NaH2PO4,  H2O, 
are  formed.  All  these  salts  give,  with  silver  nitrate,  the  same  pre- 
cipitate of  Ag3PO4. 

243.  If  these  three  sodium  salts  be  heated  until  they 
become  dry,  the  water  of  crystallization  will  be  expelled. 

On  heating  them  to  redness,  the  first  will  lose  a  molecule  of 
water  and  become  sodium  pyrophosphate. 

2(Na2HPO4)  ignited  =  Na4P2O7  +  H2O.« 

The  second  will  suffer  no   further  change;    the  third  will  lose  two 
molecules  of  water  and  become  sodium  metaphosphate. 

NaH2P04  ignited  =  NaPO3  +  H2O. 

If  these  residues  are  again  dissolved  in  cold  water,  and  a  solution 
of  silver  nitrate  added,  they  will  yield:  (1)  white  Ag4P2O7,  (2) 
yellow  Ag3PO4,  (3)  white,  gelatinous  AgPO3 — showing  the  pro- 
duction in  the  first  of  pyrophosphoric  acid,  in  the  third  of  meta- 
phosphoric  acid:  the  orthophosphoric  acid  of  the  second  remaining 
unaltered,  because  no  part  of  its  base  was  volatile. 

If  these  silver  precipitates  be  suspended  in  water,  and  a  stream 
of  hydrogen  sulphide  be  passed  through  the  liquid,  black,  insoluble 
silver  sulphide  will  be  formed,  and  the  solutions  of  the  different 
phosphoric  acids  may  be  obtained. 

The  meta-  and  pyro-phosphoric  acids  are  converted  into  the 
orthophosphoric  acids  by  prolonged  boiling  with  water. 

244.  Tests.     Orthophosphoric    acid    is    estimated    by 
adding  to  its  solution  a  mixture  of  magnesium  chloride, 
ammonium   chloride,  and   ammonia.     There  precipitates 
white  Mg",  NH4PO4,  which   becomes,  on   ignition,  Mg2 
P2O7.     The    acids    are   distinguished  from   one   another 
by  their  reactions  with  silver  nitrate  and  albumen. 


148  CHEMISTRY. 

245.  Uses.     Phosphoric  acid  is  used  in  calico  printing. 
The  superphosphate  of  lime  is  used  as  a  fertilizer. 

ARSENIC. 

246.  Arsenic  is  found  native;  in  combination  with  sul- 
phur, as  realgar,  As2S2,  and  orpiment,  As2S3  ;  but  more 
frequently  in  combination  with  the  metals,  as  arsenides. 
The  chief  sources  of  arsenic  and  its  compounds  are  iron 
arsenide,  FeAs2,  and  arsenical  pyrites,  FeS2FeAs2.    It  is 
widely  diffused,  being  found  in  small  quantity  in  many 
metallic  sulphides  and  the  products  obtained  from  them. 

247.  Preparation.     The    element    arsenic    is    obtained 
from  arsenical  pyrites  by  roasting  it  in  horizontal  tubes. 
The  arsenic  is  volatilized,  and  is  then  condensed  in  the 
cooler  portions    of  the    tubes.     It    is    also    obtained    by 
heating  arsenious  anhydride  with  charcoal.    This  process 

may  be  illustrated  by  one  of  the  methods 
•\JJH§\r^       employed  in  testing. 

i^          Exp.  154. — Introduce  into  a  small  tube  of 
hard  glass  a  little  dry  arsenious  oxide,  and  place 
above   this   a   few    splinters   of  charcoal.     First 
heat  the  coal  to  ignition,  and  then  the  arsenious 
j,-I(.   7.,  oxide.     As  its  vapor  passes  through  the  coal  it 

is    reduced,    and   condenses   as   a   shining   black 
ring  on  the  colder  portion  of  the  tube. 

248.  Physical  properties.    Arsenic  is  a  brittle  solid  of  a 
steel-gray  color  and  metallic  luster.    It  volatilizes  without 
fusing,  at  180°  C.,  and  emits  a  peculiar,  garlic-like  odor. 
Its  vapor  density  is  double  its  atomic  weight,  and  hence, 
like  phosphorus,  its  molecule  contains  four  atoms. 

249.  Chemical  properties.    Arsenic  oxidizes  in  moist  air, 
especially  when  heated.     At  a  red  heat  it  burns  with  a 
bluish  white  flame,  and  evolves  white  clouds  of  arsenious 
oxide.     It  is  spontaneously  combustible  in  chlorine,  and 
combines  readily  with  bromine,  iodine,  and  sulphur. 


ARSENETTED  HYDROGEN.  149 

When  powdered  arsenic  is  exposed  to  the  air  it  forms 
a  black  powder  which  is  sold  under  the  name  of  cobalt, 
or  "  fly  poison."  All  the  compounds  of  arsenic  are  irri- 
tant poisons.  The  best  antidote  is  prepared  by  precip- 
itating ferric  chloride  with  caustic  magnesia. 

250.  Arsenetted  hydrogen,  H3As,  derives  its  chief  in- 
terest  from    the   fact  that  its  production  allows  the  de- 
tection   of  any    soluble    form    of  arsenic,   even    in   very 
minute   quantities.-    It  is  a   colorless,  coercible  gas:    sp. 
gr.  2.7.      It    has    an    alliaceous    odor,    and,    even    when 
largely  diluted,  is  exceedingly  poisonous. 

251.  Chemical  properties.     It  burns  in  the  air  with  a 
livid  flame,  producing   arsenious   anhydride   and    water. 
It    is    decomposed    at    a    red    heat    into    hydrogen    and 
arsenic.     When  passed  into  a  solution  of  silver  nitrate, 
it  precipitates  metallic  silver   and    forms  arsenious  acid. 
6  AgNO3  +  H3As  +  3H2O  =  6  Ag  +  6HNO3  +  II3AsO3. 


252.    Marsh's   test  for  arsenic  is  conveniently  applied 
by  the  apparatus  shown  in  Fig.  73. 

Exp.  155. — A  is  a  two-necked  bottle;    D,  a  drying  tube  con- 
taining potassium  hydrate  and  calcium  chloride;  C,  a  tube  of  hard 


150  CHEMISTRY. 

glass  contracted  at  one  or  two  points  and  terminating  in  a  vertical 
jet;  Ag,  a  solution  of  silver  nitrate. 

To  study  the  properties  of  the  gas,  let  a  handful  of  granulated 
zinc  be  put  in  the  bottle  and  then  covered  with  dilute  sulphuric  acid. 
After  the  air  has  been  expelled  from  the  apparatus,  the  jet  of  hydro- 
gen may  be  lighted.  It  should  burn  with  an  almost  colorless  flame. 

Now  pour  a  little  of  a  solution  of  arsenious  acid  in  boiling 
water  down  the  funnel  tube.  Notice,  (1)  the  burning  jet  will 
change  its  color  to  a  bluish  white;  (2)  a  cold  porcelain  plate  held 
in  the  flame  will  acquire  a  dark,  metallic  spot;  (3)  obtain  several 
of  these,  and,  while  doing  so,  heat  the  tube,  C,  in  one  or  more 
places  by  the  full  flame  of  a  good  lamp.  The  white  color  will 
disappear  from  the  burning  jet,  and  a  ring  of  metallic  arsenic  be 
formed  in  the  tube  a  little  beyond  the  flame  of  the  lamp.  Little 
or  no  deposit  will  then  be  formed  on  the  plate.  (4)  Again  remove 
the  lamp  and  turn  the  jet  into  the  silver  solution.  Black,  metallic 
silver  will  be  precipitated.  The  silver  solution  should  be  quite 
dilute  at  first,  and,  if  much  arsenic  is  present,  more  silver  nitrate 
added  from  time  to  time. 

To  understand  these  reactions,  we  may  suppose  the  arsenious 
acid  to  have  been  reduced  by  the  nascent  hydrogen  to  arsenic.  A 
part  of  this  remains  as  a  black  deposit  on  the  zinc,  and  another 
part  combines  with  another  portion  of  the  hydrogen,  and  escapes 
as  arsenetted  hydrogen.  The  white  fumes  which  color  the  flame 
are  arsenious  acid.  The  black  deposits  are  arsenic,  produced  by  its 
decomposition.  The  silver  solution  will  contain  arsenious  acid  in 
the  presence  of  free  nitric  acid. 

We  may  now  apply  confirmatory  tests.  To  the  spots  on  porce- 
lain, (1)  add  a  fresh  solution  of  an  alkaline  hypochlorite — the  spots 
will  disappear:  (2)  add  ammonium  sulphide — it  will  very  slowly 
change  to  yellow  arsenious  sulphide.  Now  make  several  closed 
tubes  of  the  tube,  C.  (3)  Heat  one  of  these  tubes,  and  notice  that 
the  ring  may  be  driven  from  one  part  to  another.  (4)  Add  a  little 
nitric  acid — the  black  ring  will  be  dissolved.  Apply  any  of  the 
tests  for  arsenic  acid  to  the  solution.  (5)  Filter  the  silver  solution, 
and  carefully  add  just  enough  ammonia  to  neutralize  the  free  nitric 
acid.  If  any  undecomposed  silver  nitrate  remains,  a  yellow  pre- 
cipitate of  silver  arsenite,  Ag3AsO3,  will  form;  or  it  will  form  on 
the  addition  of  more  silver  nitrate/*  Finally,  try  Exp.  156. 

*  A  more  expeditious  method  consists  in  the  substitution  of  sodium  amalgam 
for  the  zinc:  no  acid  is  required.  Slips  of  paper  moistened  with  silver  nitrate, 
and  held  over  the  gas  which  escapes,  will  blacken  if  only  T^-i_^  grain  of  arsenic 
is  present. 


ARSENIOUS  ANHYDRIDE.  151 

253.  If  all   of  these  tests  can  be  obtained,  there  can 
be    little    doubt  of  the   presence   of  arsenic.     In  toxico- 
logical  examinations  others  must  also  be  had.     So,  also, 
the  materials  used  must  be  tested,  to  determine  that  no 
arsenic  is  present  in  them. 

This  is  done  by  subjecting  the  hydrogen  which  is  at  first  evolved 
to  the  same  tests  for  at  least  fifteen  minutes  before  adding  the  sus- 
pected substances.  It  should  be  added  that  these  substances  must 
be  previously  freed  from  organic  matters.  If  the  liquid  contains 
free  nitric  acid,  a  solid  arsenetted  hydrogen,  H2As,  is  formed  in 
the  flask. 

254.  The  oxygen  compounds  of  arsenic.     Arsenic  yields 
two  anhydrides  and  a  series  of  acids,  which  correspond 
to  phosphorous  and  phosphoric  acids. 

ANHYDRIDES.  ACIDS. 

Arsenious  anhydride,  As2O3.  Arsenious  acid,  H3As  O3 

C  Ortho-arsenic  acid,  H3As  O4. 

Arsenic  anhydride,  As2O5.  j  Pyro-arsenic  acid,  H4As2O7. 

(^  Meta-arsenic  acid,  II  As  O3. 

255.  Arsenious  anhydride,  As203,  is  formed  when   ar- 
senic is  burned  in  air.     It  is  prepared  in  large  quantities 
by  roasting  arsenical  pyrites  in  muffle  furnaces  through 
which  the  air  is  allowed  to  pass,  and  is  condensed  as  a 
fine,  white  powder  in  large  chambers. 

Exp.  156. — Heat  the  arsenical  deposit  in  a  portion  of  the  tube, 
G  (Fig.  73),  leaving  both  ends  open  to  admit  air.  The  black  ring 
will  volatilize  and  again  condense  to  white,  crystalline  As2O3. 

256.  Physical   properties.     Arsenious   anhydride   is   a 
white,  tasteless  solid  :  sp.  gr.  3.7.     The  powder  which  is 
sold  under  the  name  of  white  arsenic,  or  ratsbane,  is  its 
usual  form ;   but  it  can  also  be  obtained  by  fusion  as  a 
glassy  mass,  which  soon  becomes  opaque  like  porcelain. 
By  boiling  for    several    hours,    100   parts    of  water   can 
dissolve  11.5  parts  of  the   anhydride.     The  solution,  on 
cooling,  deposits  9   parts  as  octahedral  crystals,  leaving 


152  CHEMISTRY. 

2.5  parts  dissolved.  It  is  rather  more  soluble  in  hydro- 
chloric acid  ;  but,  on  boiling  with  hydrochloric  acid,  arse- 
nious  chloride,  AsCl^,  'is  formed  and  volatilizes. 

257.  Chemical  properties.     No  definite  hydrate  of  the 
acid    has    been    obtained.     It    forms,    however,  with   the 
metals,  well  marked  arsenites.     Fowler's  solution  is  po- 
tassium arsenite,  made    by  boiling   the    anhydride    in    a 
solution  of  potassium  carbonate.     Arsenious  acid  acts  as 
a  reducing  airont  when  heated  with  nitric  acid  and  other 

c">          O 

bodies  rich  in  oxygen,  and  is  itself  converted  to  arsenic 
acid,  As9O5.  If  heated  with  charcoal,  phosphorus,  and 
similar  reducing  agents,  it  is  reduced  to  the  element 
arsenic,  and  acts  as  an  oxidizing  agent. 

258.  Uses.     As  an  oxidizing  agent,  it   is    used    in    the 
manufacture   of  glass  to  convert  ferrous  to  ferric  oxide. 
It  is  also  used  in  the  manufacture   of  shot  and   of  sev- 
eral green  pigments.     An  arsenical  soap,  containing  ar- 
senious   acid    and    camphor,    is    used    by    naturalists   for 
preserving  the  skins  of  animals. 

TESTS. — Neutral  solutions  of  the  alkaline  arsenites  give  a  green 
precipitate  (Scheele's  green)  with  cupric  sulphate,  and  a  yellow 
precipitate  with  silver  nitrate. 

Kcinsch's  test  is  made  by  acidulating  the  acid  or  its  compounds 
with  hydrochloric  acid,  and  heating  the  mixture  gently  after  the 
addition  of  a  bright  copper  strip.  After  a  little  while,  a  steel-gray 
coating  of  Cu5As2  is  formed. 

259.  Physiological    properties.      Although    two    deci- 
grammes of  arsenious  acid  are  sufficient  to  destroy  life, 
it  is  possible  gradually  to  accustom  the  human  body  to 
daily  doses  of  three  decigrammes,  or  even  more.     As  a 
medicine,  small  doses  of  arsenious  acid  are  used  in  inter- 
mittent fevers  and  in  skin  diseases. 

260.  Arsenic   acid  is  prepared  by  oxidizing  arsenious 
anhydride  with  nitric  acid.    On  evaporating  the  solution 


ARSENIC  ACID,  153 

to  a  syrup,  deliquescent  crystals  of  3H2O,  As2O5  -j-  H2O 
are  deposited  in  rhomboidul  lamina).  These  crystals, 
heated  to  100°  C.,  lose  the  water  of  crystallization  and 
become  the  tribasic  acid  (3II2O,  As2O5) :  at  1GO°  C., 
pyro-arsenic  acid  (2H2O,  As2O5) ;  at  260°  C.,  meta- 
arsenic  acid  (H2O,  As2O5)  ;  at  a  dull  red  heat,  arsenic 
anhydride  (As2O5),  which  decomposes  at  a  full  red 
heat.  All  these  bodies  dissolve  in  water  and  yield  the 
trihydrate. 

261.  Properties.     Arsenic  acid  appears  to  be  less  poi- 
sonous  than    arsenious   acid,  but  its  acid  properties  are 
more  marked.     It  is  largely  used  in  calico  printing  and 
in  the  manufacture  of  aniline  colors. 

TESTS. — Arsenic  acid  yields  a  brick-red  silver  arseniate,  Ag3AsO4, 
with  silver  nitrate.  It  forms  many  precipitates  which  closely  re- 
semble those  of  the  tribasic  phosphoric  acid.  The  ammonio-mag- 
nesian  mixture  gives  white  Mg/xNH4AsO4,  which  is  used  for  the 
quantitative  determination  of  arsenic. 

Arsenic  acid  and  its  salts  are  reduced  by  boiling  with  sulphurous 
acid.  They  then  yield  the  tests  for  arsenious  acid. 

All  compounds  of  arsenic  in  acid  solutions  yield,  with  sul- 
phuretted hydrogen,  a  yellow  precipitate  of  As2S3;  but  it  must 
be  noted  that  with  the  higher  compounds  the  precipitate  forms 
slowly,  and  generally  only  after  heating. 

262.  The   principal  sulphides   of  arsenic  are  realgar, 
or    red    orpiment,    As2S2  ;    yellow    orpiment,    or    king's 
yellow,    As2S3 ;    and    the    penta-sulphide,    As2S5.      The 
first   two    are  found   native,   but  all   are   prepared   arti- 
ficially. 

Realgar  is  used  in  pyrotechny.  One  part  of  realgar  mixed  with' 
3.5  parts  of  sulphur  and  14  of  saltpeter  yields  a  beautiful  white 
flame  (Indian  fire). 

The  other  two  are  interesting  because  they  form  soluble  com- 
pounds with  the  alkaline  sulphides.  These  compounds  are  sulpho- 
salts  which  are  analogous  to  the  oxy-salts,  and,  hence,  As2S3  is 
sometimes  called  sulpharsenious  acid,  and  As2S5,  sulpharsenic  acid. 


154  CHEMISTRY. 

Sulpharsenious  acid  is  the  yellow  precipitate  formed  by  passing 
H2S  into  an  acidified  solution  of  the  arsenites.  The  same  com- 
pound mixed  with  free  sulphur  is  formed  by  treating  arsenic  acid 
with  H2S.  It  forms  slowly  in  cold  solutions;  more  rapidly  on 
boiling. 

If,  however,  sodium  arseniate  is  saturated  with  H2S,  a  soluble 
sulpharseniate  of  sodium,  2Na2S,  As2S5,  forms.  Hydrochloric  acid 
added  to  this  solution  precipitates  the  yellow  As2S5. 

Either  of  these  sulpho-acids  is  soluble  in  ammonium  carbonate. 


ANTIMONY. 

263.  Antimony  is  found  native,  but  generally  in  com- 
bination with  oxygen,  sulphur,  and  certain  metals. 

264.  Preparation.     The  antimony  of  commerce   is   ob- 
tained from  stibnite,  Sb2S8,  by  fusing  it  with  scrap  iron: 
Sb2S3-f  3Fe  — 3FeS  +  2Sb.     The  product  is  crude  an- 
timony, which  is  purified  by  a  second  fusion  with  sodium 
carbonate.     Pure  antimony  may  be  obtained  for  experi- 
mental   purposes    by    heating    tartar    emetic    to    bright 
redness  in  a  covered  crucible. 

265.  Physical  properties.    Antimony  is  a  brittle,  crys- 
talline metal  of  lustrous,  bluish  white  color:  sp.gr.  G.7. 
It  melts  at  450°  C.,  and   volatilizes   at   red    heat.     The 
antimony  which    is   obtained    by   electrolysis   sometimes 
has  the  curious  property  of  exploding  when   heated   or 
struck. 

266.  Chemical  properties.     Antimony  is  not  oxidized 
in  air  at  ordinary  temperatures,  but,  when  heated  above 
its   melting   point,  oxidizes   rapidly,  arid,  at  a  red  heat, 
burns  with  a  white  flame. 

Exp.  157. — Heat  a  lump  of  the  pure  metal  on  charcoal  before 
the  blowpipe.  Dense,  white  fumes  will  be  given  off.  These  are 
antimonious  oxide,  Sb2O3.  Allow  the  molten  mass  to  cool  before 
it  is  completely  burnt  away.  It  will  become  covered  with  a  crys- 
talline network  of  the  same  oxide. 


COMPOUNDS  OF  ANTIMONY.  155 

267.  Uses.     Antimony  forms  alloys  with   most   of  the 
heavy  metals,  rendering  them  harder,  more  brittle,  and 
frequently    suitable    for    forming    sharp    casts.     Among 
these  are  type  metal  (Sb  and  Pb),  Brittania  metal,  and 
pewter  (Sn  and  Sb). 

268.  The  compounds  of  antimony.  —  (I)  The  chlorides. 
Finely  powdered    antimony  takes   fire   spontaneously  in 
chlorine  gas,  forming   either   SbCl3  or  SbCl5,  according 
as  the  antimony  or  chlorine   is   in   excess.     Hence,  if  a 
slow  current  of  chlorine  be  passed  through  a  tube  con- 
taining  antimony,  antimoriious  chloride,  SbCl3,  will   be 
formed.     This  condenses  as  a  soft,  gray  solid  known  as 
the  butter  of  antimony.     It   is   also   formed  when    anti- 
monious  sulphide  is  boiled  with  hydrochloric  acid. 

If  chlorine  gas  be  passed  over  antimonious  chloride, 
a  yellowish,  volatile  liquid  forms,  which  is  antimonic 
chloride,  SbCl5. 

(II)  Oxides.     Both  of  these  chlorides  are  decomposed 
when   added   to   a   large   quantity  of  water.     The   first 
yields   a    white   powder,    the    oxychloride    of  antimony 
(SbCl3,  Sb2O3) ;    the    second,    white    metantimonic    acid 
(2H2O,  Sb2O5).     If  these    two   precipitates    are    gently 
heated,  they  form  antimonious   oxide,  Sb2O3,  and  anti- 
monic oxide,  Sb2O5.     When  either  of  these  is  strongly 
heated,  a  yellow  powder  is  formed  which  is  probably  a 
mixture  of  both  :    Sb2O3,  Sb2O5  =  2Sb2O4. 

(III)  Acids.     These    oxides    of  antimony    dissolve    in 
alkaline  solutions  to  form  antimonites  and  antimonates. 
They  may  also  be  obtained   as   antimonious  acid,  H2O, 
Sb2O3  ==  HSbO2,    and    antimonic    acid,    H2O,  Sb2O5  = 
2(HSbO3).      This    last    corresponds    to    metaphosphoric 
acid.     There  is  also  a  tetrabasic  acid,  H4Sb2O7,  which 
is   called  metantimonic    acid.      It   corresponds   to   pyro- 
phosphoric    acid.      Potassium    metantimoniate    is    some- 
times used  in  testing  for  sodium. 


156  CHEMISTRY. 

269.  Antimonious   oxide  acts   not   merely  as  an   acid, 
but   also   as  a  basic   anhydride.     It  readily  dissolves  in 
tartaric   acid   to  form  antimonious  tartrate.     It  also  dis- 
solves  readily   in    acid    potassium   tartrate,  and  thereby 
forms  the  well-known  tartar  emetic: 

Sb208  or  (SbO),0  +  2(KH,C4H406)  = 

2(K,SbO,C4H406)  +  H20. 

In  these  cases  we  may  suppose  it  to  be  represented  by 
the  radical  antimony!  (SbO)'. 

270.  Tests.     When   a   stream  of  hydrogen  sulphide  is 
passed  through  acidulated  solutions  containing  the  com- 
pounds of  antimony,  sulphides  of  antimony  are  formed 
which  are  sulpho-acids  similar  to  those  of  arsenic.    The 
antimonic  compounds  yield    a   yellowish   red    antimonic 
sulphide,  Sb2S5  ;  the  antimonious  compounds,  orange  red 
antimonious  sulphide,  Sb2S3,  soluble  in  ammonium  sul- 
phide.    Both   of  these  dissolve  in  hot  hydrochloric  acid 
as  chlorides,  which  are  decomposed  by  a  large  quantity 
of  water— SbCl6  yielding  II4Sb2O7;  SbCl3,  a  white  oxy- 
chloride,  SbCl3,  Sb2O3,  or  SSbOCl,  soluble  in  tartaric  acid. 

Marsh's  test  yields,  with  the  compounds  of  antimony,  an  odor- 
less, antimonetted  hydrogen,  H3Sb.  which  gives  reactions  similar 
to  those  observed  with  arsenic.  They  are,  however,  easily  distin- 
guished. (1)  The  metallic  deposits  are  darker  and  are  less  volatile 
than  those  of  arsenic.  (2)  They  are  insoluble  in  alkaline  hypo- 
chlorites  which  do  not  contain  free  chlorine.  (3)  Gently  warmed 
with  nitric  acid,  they  are  oxidized  but  not  dissolved.  The  anti- 
monious oxide  formed  yields  black  Ag4O,  with  neutral  silver  nitrate 
and  ammonia.  (4)  They  arc  readily  soluble  in  ammonium  sulphide. 
(5)  The  deposit  in  the  silver  solution  is  black  Ag3Sb,  silver  anti- 
monide;  hence,  if  any  precipitate  forms  in  the  solution  when  fil- 
tered on  the  addition  of  ammonia,  it  is  the  oxide  of  silver. 

Keinsch's  test  yields  purple  copper  antimonide. 

271.  Uses.    Antimonious  chloride  is  used  for  bronzing 
gun  barrels.    Antimonious  sulphide  is  used  in  the  prepa- 
ration of  blue  signal  lights  (Bengal  light).     Tartar  emetic 
is  used  in  medicine. 


BISMUTH.     /  157 

BISMUTH. 

272.  Bismuth   is   found   chiefly  in   the  metallic   state, 
and   is   freed  from  its  earthy  impurities  by  heating  the 
ore  in  iron  cylinders  which  are  fixed  in  an  inclined  posi- 
tion over  a  furnace.  (Fig.  74).  The  bismuth  melts  at  264° 
C.,  and  runs  out  at  the  lower  ends 

of  the  tubes  into  iron  vessels. 

273.  Physical   properties.     Bis- 
muth is  a  brittle  metal  of  a  red- 
dish  luster:    sp.  gr.  9.8.     It   may 
be  obtained  in  beautiful,  rhombo- 
hedral  crystals  by  melting  several 
pounds  of  it,  allowing   it   to   cool 
till  a  crust  has  formed  on  its  sur- 
face, and  then  pouring  out  the  metal  which  still  remains 
molten.     The  crystals  will  be  found  lining  the  interior 
of  the  crucible.     The   metal   expands  ^   in   solidifying. 
It  is  the  most  highly  dia-magnetic  substance  known. 

274.  Chemical  properties.     Bismuth   does   not   oxidize 
in    the    air   at   ordinary   temperatures.     It   burns  when 
strongly  heated  in  the  air  with  a  bluish  flame,  forming 
yellow   fumes    of  bismuthous    oxide,    Bi2O3.     It    unites 
directly   with    chlorine,    bromine,    iodine,    and    sulphur. 
It  readily  dissolves  in  nitric  acid,  forming  the  bismuth- 
ous nitrate,  Bi2O3,3N2O5  or  Bi(NO3)3. 

275.  Uses.     Bismuth  is  used,  together  with   antimony, 
in    the    construction    of   thermo-electric    batteries.     Its 
presence  in  alloys  has  a  wonderful  influence  in  lowering 
the  melting  point.     Eose's  fusible  metal  melts  at  94°  C. 
It  is  composed  of  two  parts   of  bismuth    and   one   each 
of  lead  and  tin,  or  very  nearly  Bi2PbSn4.     This  is  valu- 
able for  taking  impressions  of  dies,  inasmuch    as  it  ex- 
pands on  cooling,  and  reproduces  the  faintest  lines  with 
accuracy. 


158  CHEMISTRY. 

276.  The  compounds  of  bismuth,  —  (I)  Oxides.  If  bis- 
muthous nitrate  is  dissolved  in  a  small  quantity  of  water, 
and  added  to  an  excess  of  potassium  hydrate,  bismuthous 
hydrate  precipitates  as  3H2O,  B52O3  or  H3BiO3.  This 
body  becomes,  on  ignition,  Bi2O3,  bismuthous  oxide. 
It  seems  also  to  enter  into  compounds  as  the  mon- 
atomic  radical  (BiO)',  to  form  salts  which  are  known 
as  basic  or  sub- salts. 

Bismuthic  acid,  II2O,  Bi2O5  or  IIBiO3,  is  formed  by 
passing  chlorine  gas  through  a  hot  potash  solution  which 
contains  bismuthous  hydrate  in  suspension.  Its  acid 
powers  are  weak  and  its  salts  are  of  no  importance. 

If  bismuthous  nitrate  is  thrown  into  a  large  quantity 
of  water,  it  precipitates  a  basic  or  sub-nitrate  of  bismuth, 
Bi2O3,N2O5  or  (BiO)'NO3,  also  known  as  flake  white. 

(II)  Chlorides.     If  the  nitrate  is  poured  into  a  solution 
of  sodium    chloride,  an    oxychloride   of  bismuth,  BiCl3, 
Bi2O3  =  SBiOCl,  or   "pearl   white,"    precipitates.     This 
dissolves  in  hydrochloric   acid    to   bismuthous    chloride, 
BiCl3,  and  again  precipitates  on  the  addition   of  water. 
The  formation   of  these  basic  bodies  by  water  is  char- 
acteristic of  bismuth.     Unlike  the  similar  compounds  of 
antimony,  they  are  insoluble  in  tartaric  acid. 

(III)  Salts.      Bismuthous    carbonate,    (BiO)2CO3,    is 
formed  by  decomposing  bismuthous  nitrate  by  an  excess 
of  an  alkaline  carbonate.     This  salt  and  the  basic  nitrate 
are  used  in  medicine.     Pearl  white  is  used  as  a  cosmetic. 

TESTS. — The  salts  of  bismuth  arc  sufficiently  characterized  by 
their  decomposition  with  water.  They  form,  with  soluble  sulphides, 
black  precipitates  which  are  bismuthous  sulphide,  Bi2S3. 

Recapitulation. 

Review  sections  190,  191,  and  193. 

This  group  contains  all  the  pentad  elements.     Although  the  mem- 
bers of  the  group  exhibit  marked  differences,  they  also  exhibit 


RECAPJTULA  TION. 


159 


a  marked  gradation  of  properties,  which  will  be  best  shown  by 
dividing  them  into  sub-groups,  as  follows: 


I 

ii 

in 

IV 

v 

N  14 

P     31 

P     31 

P     31 

As  75 

P   31 

V    51 

As  75 

Sb  122 

Sb   122 

V  51 

As  75 

Sb  122 

Bi   210 

Bi   210 

Note  that  the  atomic  weight  of  the  middle  clement  in  each  of  these  sub  groups 
is  very  nearly  the  mean  of  the  other  two.  In  each  of  these  sub-groups  the  middle 
etcment  also  exhibits  more  or  less  resemblance  to  the  first  and  third,  and  may 
be  said,  in  a  general  sense,  to  form  a  connecting  link  between  them. 

Among  the  numerous  points  to  be  noticed  are: 

(1)  Nitrogen  is  generally  a  gas;   phosphorus,  a  vitreous  solid;  and 
vanadium,  a  semi-metal.     The   nitrogen    compounds   are  easily 
decomposed;  the  phosphorus  compounds  are  exceedingly  pliant, 
changing   readily   from   one   form   to  another.     These  qualities 
fit  them  for  the  laboratory  of  nature,  and  we  find  them  neces- 
sary both  to  vegetables  and  animals. 

(2)  The   pentoxides    of  the   second   sub-group   yield  ortho-,  pyro-, 
and  meta-  "ic:)  acids,  which  form  "#te"  salts  that  are  isomor- 
phous  and  generally  agree  in  their  properties. 

(3)  The   elements   of  the  third  sub-group  are  either  poisonous  (P) 
or   form   poisonous  compounds  (As  and  Sb).     Sb   alone   forms 
no  ortho-,  oxy-acid.     The  molecule  of  P  and  of  As  contains  4 
atoms;  that  of  Sb  has  not  been  determined. 

(4)  The  oxides  of  the  fourth  sub-group  form  a  decreasing  series  as 
regards  their  acid  properties.     Those  of  P   are   generally  acid 
anhydrides;  Sb2O3  is  either  acid  or  basic;  Sb2O5,  acid;  Bi2O3, 
basic;    and  Bi2O5,  feebly  acid. 

(5)  The  sulphides  of  the  fifth  sub-group  are  all  sulpho-anhydrides, 
which  form  with  sulphides  of  many  metals  sulpho-salts  analo- 
gous to  the  oxy-salts. 

The  formula  of  the  chloride  of  nitrogen  is  unknown.  All  the  ter- 
chlorides  of  the  remaining  elements  are  decomposed  by  water, 
forming  generally  oxy-chlorides  of  the  formula  (KO)  Cl.  (See 
also  §  212).  Imagine  in  these  compounds  the  chlorine  to  be 
removed;  there  will  remain  a  monatomic  radical  of  the  for- 
mula (WO")',  which  is  represented  in  (SbO)',  (A&O)',  and 
probably  by  (BiO)/  in  basic  bismuthous  compounds. 


CHAPTER    V11I 


BORON. 

Symbol,   B:     Atomic  weight,  11.     Specific  gravity,  2.68. 
Melts   about   300°  C.     Isolated  by  Gay-Lussac  in   1808. 

277.  Boron  is  a  triad  element  which  derives  its  chief 
importance  from  boracic  or  boric  acid,  II2O,  B2O3  or 
IIB02. 

Borax  (Xa2O,  2B2O8,  10II2O  or  Na2B4O7,  10II2O)  is 
found  native  as  tincal  in  certain  lakes  of  Asia  and  Cal- 
i'fornia.  Boric  acid  is  found  native  as  sassolite.  It  is 
principally  obtained  from  the  volcanic  districts  of  Tus- 
cany. 


FIG.  75. 

In  that  country  numerous  jets  of  steam,  called  sujfoni,  issue  from 

fissures  in  the  ground,  and  are  condensed  into  natural  or  artificial 

ponds  called  lagunes.     The  water   in   these  lagunes  contains  dilute 

boric  acid;  and,  on  evaporation,  which  is  carried  on  by  the  natural 

(160) 


BORON.  161 

heat  of  the  suffoni,  yield  a  crude  boric  acid.  This  is  either  purified 
by  re-crystallization  or  is  employed  in  the  manufacture  of  borax. 
Pure  boric  acid  may  be  obtained  from  borax. 

Exp.  158.— Boil  3  parts  of  borax  in  12  of  water,  and  to  the 
hot  solution,  filtered  if  necessary,  add  1  part  of  strong  sulphuric 
acid.  On  cooling,  boric  acid  separates  in  white,  pearly  looking 
scales,  unctuous  to  the  touch.  These  are  the  orthoboric  acid,  3H2O, 
B2O3.  When  heated,  they  are  converted  to  pyroboric  acid,  H2B4O7; 
then  to  metaboric  acid,  HBO2;  and  finally  to  the  anhydride  B2O3, 
which  fuses  to  a  transparent  glass. 

278.  Boric  acid  is  soluble  in  25  parts  of  water  at 
18°  C.,  and  in  3  parts  at  100°  C.  It  must  be  reckoned 
as  a  feeble  acid :  its  solution  colors  litmus  a  dark  wine 
red,  and  turmeric  a  brown  red.  At  high  temperatures, 
fused  boric  acid,  and  also  borax,  dissolves  many  metallic 
oxides  to  form  transparent  glassy  borates.  Hence  they 
are  employed  as  fluxes  in  soldering,  and  are  often  added 
to  enamels  to  render  them  more  fusible.  Large  quanti- 
ties of  borax  are  used  in  glazing  stone-ware. 

Exp.  159. — Bend  the  end  of  a  thin  platinum  wire  into  a  small 
loop.  Heat  this  and  touch  it  to  a  small  fragment 
of  dried  borax.  The  borax  will  adhere  to  the 
wire.  Now  introduce  the  borax  into  the  flame 
of  a  Bunsen's  lamp.  It  will  fuse  to  a  clear 
glassy  bead. 


Very    small    quantities    of   several    of 
the  metallic  oxides  produce  characteristic 
colors  when  they  are  added  to  the  borax 
bead,  and  hence  these  beads  are  often  used  in  blowpipe 
testing. 

Exp.  160. — Just  touch  the  borax  bead  with  cobalt  nitrate;  then 
melt  the  bead  again.  It  will  become  a  beautiful  blue.  Manganese 
gives  an  amethyst  bead  in  an  oxidizing  flame;  chromium,  and 
copper,  a  green  bead;  ferric  oxide  gives  a  greenish  yellow  bead. 
Many  oxides,  like  those  of  silver,  nickel,  and  lead,  yield  grayish 
beads  in  the  reducing  flame,  owing  to  the  presence  of  the  reduced 
metal. 

Chem.-ll. 


162  CHEMISTRY. 

279.  Test.     Boric  acid   is   detected  by  its  imparting  a 
a  green  color  to  flames. 

Exp.  161.  —  (I)  Dissolve  a  little  boric  acid  in  alcohol,  and 
ignite.  A  beautiful  green  flame  is  produced,  which,  when  examined 
by  the  spectroscope,  is  resolved  into  a  series  of  five  green  bands. 

(II)  Form  a  borax  bead  on  a  platinum  wire;  then  moisten  it 
with  strong  sulphuric  acid.  On  bringing  this  into  a  colorless  flame, 
the  green  flame  characteristic  of  boron  will  be  produced. 

280.  Boron  may  be  obtained  as  an  amorphous,  brown 
powder  by  heating  vitrified  boric  anhydride  with  sodium. 
It  has  also  been  obtained  as  graphitoidal  boron  in  brill- 
iant scales,  like  graphite,  and   as   adamantine   boron    in 
brilliant,  highly  refracting  crystals  which    resemble  the 
diamond  both  in  their  luster  and  hardness.    These  latter 
are    thought    to    be   allotropic   forms   of  boron  ;   but  the 
adamantine    always    contains    carbon,    and    the    graph- 
itoidal, aluminum. 

Its  physical  properties  strongly  resemble  those  of 
carbon  and  silicon,  with  which  it  was  formerly  classed. 
All  form  feeble  acids  by  direct  union  with  oxygen, 
whose  salts  also  frequently  resemble  each  other.  Their 
relationship  may  be  expressed  graphically  thus: 


C/r12 


Recapitulation, 

Boron  is  the  only  triad  in  the  list  of  the  non-metals. 
Its  principal  salt  is  borax. 


CHAPTEK    IX. 

THE    CARBON    GROUP. 


. 

H 

0° 

W 

£ 

• 

2 
3 

g 
O 

X 

p 

ELEMENT. 

4 

o 

O 

fe 

PH 

O 

DISCOVERER. 

§ 

g 

i 

% 

B 

cc 

<! 

00 

^ 

Carbon 

c 

12 

3.33 

Silicon 

Si 

28 

2.49 

Berzelius,   1823. 

Titanium 

Ti 

50 

5.3? 

Gregor,       1791. 

Zirconium 

Zr 

89.6 

4.15 

Klaproth,  1789. 

Tin 

Sn    i  118 

7.29 

230° 

i 

281.  This  is  a  group  of  tetrad  elements.  All  of  them 
unite  with  four  atoms  of  chlorine  to  form  tetrachlorides. 
Carbon  and  silicon  form  gaseous,  inflammable  compounds 
with'  four  atoms  of  hydrogen,  as  CH4  ;  SiH4.  All  of 
the  elements  in  this  group  form  dioxides  and  disulphides, 
which  unite  as  acids  with  the  alkaline  oxides  and  sul- 
phides to  form  oxy-  and  sulpho-salts,  as  K2O,  CO2 ; 
K2S,  CS2  ;  or  K2C03  and  K2CS3. 

Carbon  and  tin  also  act  as  dyads  in  a  few  compounds ; 
as  CO,  SnCl2,  SnO,  SnS.  These  compounds  are  either 
indifferent  bodies,  or  they  possess  feebly  basic  properties. 

Carbon  and  silicon  are  non-metals  whose  physical 
properties  resemble  those  of  the  triad  element  boron. 
One  of  their  allotropic  conditions,  the  graphitoidal,  has 
some  of  the  physical  characters  of  the  metals,  viz,  their 
luster  and  the  property  of  conducting  heat  and  elec- 
tricity. 

(163) 


164  CHEMISTRY. 

Zirconium,  titanium,  and  tin  arc  semi-metals  very 
closely  resembling  each  other,  and  are  allied  in  their 
physical  properties  to  the  metals. 

282.  Carbon  is  remarkable   for  the  great   number  of 
its  hydrogen  compounds.     These  arc  spoken    of  collect- 
ively as  the  hydrocarbons,  and  include  the  greater  number 
of  the    essential   oils,  coal  oils,  and  the  gases   used   for 
illumination.     They  are  generally  classed   together   and 
studied    in    organic   chemistry,  which  may  be   defined   as 
the    "  chemistry   of  the   carbon    compounds."     Only  the 
oxides  and  sulphides  will  be  presented  in  this  chapter. 

CARBON. 

283.  Carbon   is   one    of  the   most  abundant  elements. 
In  combination  it  is  an  essential   constituent   of  all    or- 
ganic   substances ;    of  all    carbonates,  such  as  limestone, 
and  is  found  in  the  air  in  carbonic  anhydride.     In   the 
free    state    it   occurs  in  three  allotropic  forms :    (1)  pure 
in   the  diamond;    (2)  nearly  pure  in  graphite;    and  (3) 
less    pure    in    anthracite    coal.     Carbonado,    gas   carbon, 
coke,    lampblack,    and    charcoal    are    varieties    of  these. 
Bituminous  coal,  asphalt,  and  jet  contain  also  hydrocar- 
bons which  are  volatilizable  by  heat. 

Physical  Properties  of  Carbon. 

284.  (I)  The  diamond  occurs  as  small,  rounded  bodies 
in    the    detritus   of  certain    quartzose    rocks    which    are 
found  principally  in  Golconda,  Brazil,  and  South  Africa. 
Its  crystalline  form  is  that  of  the  octahedron :  sp.  gr.  3.5. 
It  has   a  brilliant  luster,  which  is  increased  by  cutting 
so  as  to  furnish   numerous  facets   capable  of  reflecting 
and    refracting    light    in    various    directions.     It   is   the 
hardest  substance  known,  and  hence  can  be  cut  only  by 
means  of  dust  obtained  by  pounding  up  the  least  valu- 
able  sorts   of  diamonds.     When    broken,    the    diamond 


GRAPHITE.  165 

naturally  cleaves  in  directions  nearly  parallel  to  other 
faces  of  the  octahedron,  but  generally  in  faces  more 
or  less  curved.  These  curved  faces  intersect  in  curved 
edges,  which  are  more  suitable  than  straight  edges  for 
cutting  glass,  as  they  are  capable  of  penetrating  the 
glass  like  a  wedge,  instead  of  merely  scratching  its 
surface. 

The  carbonado,  a  black  diamond  found  in  Brazil,  has 
lately  been  employed  in  rock  cutting  to  great  advantage. 

285.  (II)    Graphite   is   occasionally  found   in  six-sided 
plates   which    belong   to   the   rhombohedral   system.     It 
generally  occurs  in  the  amorphous  state,  and  is  known 
as  plumbago   or   black  lead :    sp.  gr.  2.2.     Graphite   has 
a  dark,  steel-gray  color,    a   semi-metallic    luster,    and   is 
unctuous    to   the    touch.     It   is    found  generally  in    the 
older    rocks,    and    occurs    most    abundantly    in    Ceylon, 
Siberia,  and  California.     The  graphites   of  Cumberland, 
England,  and  of  Ticonderoga,  "N.  Y.,  are  especially  noted 
for  their  purity.     Some  varieties  of  cast  iron  contain  so 
much  graphite  that  it  separates  in   the  crystalline  form 
(kisTi)  w^hen  the  molten  iron  is  slowly  cooled. 

Graphite  is  used  for  making  lead-pencils  and  crucibles,  for  pol- 
ishing stoves,  and  as  a  lubricant  to  diminish  the  friction  of  ma- 
chinery. It  is  a  conductor  of  electricity,  and  is  used  in  the  elec- 
trotype process  to  impart  a  conducting  surface  to  non-conducting 
materials,  such  as  wax. 

286.  (HI)  Mineral  coal  exists  in  three  principal  vari- 
eties :  anthracite,  bituminous,  and  lignite.     These  are  all 
undoubtedly  of  vegetable  origin;    and   it  is  possible  to 
form   a   series   beginning  with  peat,  in  which   much   of 
the    material    is    not    thoroughly    carbonized ;    through 
lignite,  in  which  the  woody  structure   is   clearly  appar- 
ent;   cannel  coal,  from  which  large  quantities  of  the  so- 
called  coal  oils  may  be  distilled ;  bituminous  coal,  which 
readily  cakes  together  when  heated,  and   burns  with   a 


166  CHEMISTRY. 

bright  blaze ;  non-caking  bituminous  coal ;  anthracite 
coal,  which  contains  90  per  cent  of  carbon  ;  to  the  coals 
of  Greenland,  which  are  sometimes  regarded  as  graphite. 

287.  (IV)  Bituminous  coals,  when  distilled,  yield  a 
large  number  of  volatile  hydrocarbons,  and  a  porous, 
often  brilliant  "looking  solid,  which  is  known  as  coke. 
It  is  an  accidental  product  in  the  manufacture  of  illumi- 
nating gas,  but  is  also  purposely  prepared  for  iron 
smelting,  to  obtain  a  fuel  that  does  not  cake  in  burning. 

Another  very  dense  and  hard  form  of  carbon,  which 
is  slowly  produced  in  gas  retorts  by  the  decomposition 
of  the  volatile  hydrocarbons;  is  known  as  gas  carbon. 
It  is  used  as  the  negative  clement  in  many  forms  of 
galvanic  batteries.  The  carbon  plates  are  usually  pre- 
pared by  compressing  a  mixture  of  coke,  coal,  and  treacle 
in  iron  moulds,  and  then  strongly  heating  the  mixture. 


(Y)  The  imperfect  combustion  of  organic  sub- 
stances also  yields  various  forms  of  carbon.  Wood  char- 
coal is  generally  made  by  piling  billets  of  wood  in  large 
heaps,  which  are  covered  with  turf, — holes  being  left  at 
the  bottom  for  the  air  to  get  in,  and  a  flue  left  open 
at  the  middle  of  the  heap.  The  heap  is  then  kindled 
at  the  center,  and,  when  the  combustion  is  well  estab- 
lished, the  flue  is  closed  and  the  mass  is  allowed  to 
smoulder  until  the  wood  is  perfectly  carbonized.  A 

better  method  con- 
sists in  heating  the 
wood  in  iron  cyl- 
inders. 


Exp.   162.  — Place 

in  a  glass  retort  splin- 
ters of  wood,  and  ar- 
range the  apparatus  as 
shown  in  Fig.  77.  On 
heating  the  retort,  in- 
flammable gases  will  collect  in  the  cylinder  over  water;  tar,  water, 


CHARCOAL.  167 

methylic  alcohol,  and  acetic  acid,  in  the  receiver;  and  charcoal  will 
remain  in  the  retort. 

The  charcoal  remaining  weighs  about  one-fourth  of  the  original 
wood.  It  retains  the  general  structure  of  the  wood,  even  to  the 
concentric  rings.  Owing  to  its  porous  nature,  it  is  capable  of  ab- 
sorbing large  amounts  of  gases;  it  absorbs  90  times  its  volume  of 
ammonia,  and  55  times  its  volume  of  sulphuretted  hydrogen.  Hence 
it  is  of  great  use  in  purifying  drinking  water,  and  as  a  deodorizer 
for  putrefying  matters.  Those  gases  are  best  absorbed  that  are 
easily  condensed,  seeming  to  indicate  that  the  absorbed  gases  as- 
sume in  part  a  liquid  condition. 

Exp.  163. — Fill  a  long  glass  tube  with  dry  ammonia  over  a 
trough  containing  mercury,  and  then  introduce  a  fragment  of  char- 
coal recently  ignited  and  cooled  under  mercury.  In  a  short  time 
the  coal  will  so  absorb  the  ammonia  that  the  mercury  will  be 
forced  up  the  tube.  (Use  apparatus  in  Fig.  1). 


(VI)  Animal  charcoal  is  made  by  heating  crushed 
bones  in  iron  retorts.  It  is  a  mixture  of  very  finely 
divided  coal  and  calcium  phosphate.  It  is  largely  used 
for  decolorizing  sugar  syrups  and  in  refining  alcohol. 

Exp.  164. — To  show  these  properties, 
shake  a  handful  of  freshly  ignited  animal 
charcoal  with  an  infusion  of  logwood:  boil, 
and  then  filter  the  mixture  through  paper. 
The  liquid  will  have  lost  its  color. 

It  is  important  to  observe  that  in 
many  cases  other  bodies  than  the 
coloring  matters  are  retained  by  the 
charcoal.  Thus,  it  removes  the  bitter 
principle  of  beer,  and,  what  is  more 

important,  most  of  the  alkaloids— as  quinine  and  strych- 
nine— from  their  solutions. 

290.  (VII)  Lampblack  is  the  soot  obtained  by  the 
imperfect  combustion  of  resinous,  tarry,  or  oily  matters, 
or  of  the  natural  gases  of  petroleum. 


168  CHEMISTRY. 

Exp.  165. — Set  fire  to  a  lump  of  resin,  and  hold  a  cold  white 
plate  over  the  flame.  Abundance  of  soot  will  be  deposited  upon  it. 

If  the  first  product  is  calcined  in  a  covered  crucible,  a  very 
nearly  pure  form  of  carbon  is  obtained.  Its  impurities,  however, 
do  not  affect  its  employment  as  a  pigment  in  the  manufacture  of 
paint,  printing  ink,  and  blacking. 

All  these  forms  of  carbon  arc  practically  infusible, 
although  it  is  stated  that,  at  the  exceedingly  high  tem- 
perature of  the  voltaic  arc,  phenomena  have  been  ob- 
served which  indicate  its  fusion  and  volatilization. 

291,  Chemical  properties.  At  ordinary  temperatures, 
all  these  forms  of  carbon  are  chemically  inert.  Manu- 
scripts written  with  an  ink  made  of  lampblack,  still 
perfectly  legible,  have  been  exhumed  with  Egyptian 
mummies.  It  is  a  common  practice  to  char  the  ends 
of  wooden  stakes  which  are  intended  to  be  sunk  in  the 
ground,  so  that  the  interior  may  be  protected  from  de- 
cay by  a  superficial  coating  of  charcoal. 

At  high  temperatures,  carbon  enters  into  direct  com- 
bination with  oxygen,  sulphur,  hydrogen,  nitrogen,  and 
a  few  of  the  metals.  Porous  wood  charcoal  ignites  in 
the  air  at  240°  C. ;  anthracite  requires  a  much  higher 
temperature ;  and  the  diamond,  the  highest  temperature 
of  all  the  forms  of  carbon.  At  very  high  temperatures, 
the  affinity  of  carbon  for  oxygen  is  so  great  that  it  is 
capable  of  removing  oxygen  from  its  compounds  with 
the  metals.  Hence,  it  is  largely  employed  as  a  reducing 
agent  by  the  metallurgist.  (See  Exp.  154). 

Exp.  166.— Mix  basic  bi.smuthous  nitrate  with  an  equal  bulk 
of  charcoal  in  fine  splinters,  and  heat  this  mixture  in  a  crucible 
to  ignition.  (For  apparatus,  gee  Fig.  07).  On  cooling,  a  bead  of 
metallic  bismuth  will  be  found  in  the  crucible.  A  little  decrepi- 
tated sodium  chloride  may  be  placed  to  advantage  on  the  top  of 
the  crucible,  so  as  to  exclude  the  air. 

Repeat  this  experiment  with  litharge. 

Heated  coal  is  even  able  to  decompose  water.     Thus, 


CARSONOVS  OXIDE. 


100 


if  steam  be  passed  over  rod-hot  charcoal  (use  apparatus 
in  Fig.  7),  the  carbon  will  unite  with  its  oxvgen,  lib- 
erating hydrogen  and  forming  earbonous  oxide  and  car- 
bonic anhydride  : 


292.  The  compounds  of  carbon  and  oxygen  are  ear- 
bonous oxide  and  carbonic  anhydride.  Uoth  are  aeri- 
form bodies,  formed  by  the  direct  union  of  the  two 
elements  when  any  form  of  carbon  is  burned  in  air. 
When  the  supply  of  air  is  abundant,  nearly  pure  car- 
bonic anhydride  is  produced;  but  when  the  supply  is 
limited,  it  is  mixed  with  carbouous  oxide. 


Carbonous 
oxide,  (A),  is  more 
frequently  known 
by  the  name  of  car- 
bonic oxide.  It  may 
be  prepared  by  gon- 
tly  heating  thor- 
oughly dried  potas- 
sium ferrocyanide 
with  four  times  its 
weight  of  sulphuric 
acid,  and  washing  ^* 
the  gas  with  a  so- 
lution of  potassium  hydraU 
be  removed  as  soon  as  the 
f-ClIjO-f  I'nII.jtfO.,) 


(Fig. 


lamp  must 


gas  begins  to  form  rapidly. 


(>CO  j  L\K3S04H   FoS04  -f  3[(II4N)aS04)]. 
It  is  also  produced  by  the  reaction  mentioned  in  $292. 

294.  Physical  properties.  Carbonous  oxide  is  a  per- 
manent, colorless  gas,  nearly  insoluble  in  water:  sp. 
gr.  0.0(57.  It  is  completely  absorbed  by  a  solution  of 
cuprous  chloride. 


170  CHEMISTRY. 

295.  Chemical   properties.     Carbohous  oxide  burns  in 
the  air  with  a  pale  blue  flame  and  forms   carbonic   an- 
hydride, CO2.     Conversely,  carbonic  anhydride  is  readily 
reduced  to  carbonous  oxide.     Thus,  when  the  air  enters 
at  the  bottom  of  a  clear  fire,  the  oxygen  at  once  unites 
with    the   carbon   to   form   carbonic  anhydride.     As  this 
gas   passes   through    the    heated    embers  above,  it  is  re- 
duced by  the  coals  to  carbonous  oxide  (CO2-{-C  — 2(5U). 
The  blue  flame  which  is  noticed  on  the  top    of   anthra- 
cite fires  is  produced  by  the  combustion  of  this  carbon- 
ous oxide  in  the  fresh  air  above  the  coals. 

Carbonous  oxide  is  a  reducing  agent.  It  may  be  cm- 
ployed  instead  of  hydrogen  to  reduce  cupric  or  ferric 
oxide  in  the  apparatus  shown  in  Figs.  7  or  27. 

The  reactions  already  mentioned  play  an  important 
part  in  many  metallurgical  operations. 

Thus,  in  the  reverbenitory  furnace  represented  in  Fig.  80,  tho 
metallic  oxides  are  placed  on  the  hearth  and  the  fuel  at  the  side. 

The  fuel  is  burned  so  as 
to  yield  carbonous  oxide, 
which  then  plays  over  tho 
hearth,  abstracts  the  oxy- 
gen from  the  ores,  and  re- 
duces them  to  the  metallic 
state.  The  production  of 

FlG  £Q  this  oxide   is   increased  by 

placing  pans  of  water  be- 
low the  bars,  so  that  steam  may  be  formed  and  produce  the  reaction 
mentioned  in  \  292. 

Carbonous  oxide  unites  directly  with  chlorine,  sulphur, 
and  potassium,  but  it  does  not  form  salts  with  either 
acids  or  bases.  It  is  regarded  as  the  free  state  of  the 
diatomic  radical  carbonyl,  and  enters  as  such  into  many 
organic  compounds. 

296.  When  carbonous  oxide  is  passed  over  hot,  moist- 
ened potassium  hydrate,  potassium  formiate  is  produced: 
KHO  4-  CO  =  KHO,  CO ;    or   KO,  CHO ;    or  H,  COOK. 


CARBONIC  ANHYDRIDE.  171 

This  is  an  interesting  reaction,  as  from  this  salt  formic 
acid,  HO,  CHO,  may  be  prepared,  an  example  of  the 
synthesis  of  organic  bodies  from  inorganic  materials. 

297.  Physiological  properties.     Carbonous  oxide  is  so 
poisonous  that  one  per  cent  of  it  diffused   through   the 
air   produces   giddiness    in    those    that   breathe    it,   and, 
after  a  while,  a  fatal  result  through  suffocation. 

298.  Carbonic  anhydride,  C02.     We  have  already  no- 
ticed  that  this  body  is  produced  by  the  complete  com- 
bustion   of  carbon    and   of  carbonous  oxide.     It   is  also 
produced  by  the  processes   of  respiration,  fermentation, 
and  decay.    As  these  processes  are  going  on  continually, 
enormous  quantities  of  carbonic  anhydride  would  accu- 
mulate in  the  air,  were  it  not  that  the  leaves  of  plants, 
under    the    influence    of  sunlight,    decompose    this    gas, 
assimilating  the  carbon  to  form  woody  tissue  and  other 
vegetable  products,  and  giving  back  the  oxygen  to  the 
air.     This  so  maintains  the  balance  of  nature   that   the 
average   quantity  of  carbonic  anhydride  in  the  atmos- 
phere  is   about   one  twenty-five  hundredth  part  of  the 
whole.     Liquors   like   champagne   and   soda  water   owe 
their  effervescing  character  to  the  carbonic  acid  which 
has  been  retained  in  them  by  pressure. 

299.  Preparation.     Carbonic  anhydride  is  usually  pre- 
pared by  the  action  of  dilute  acids  upon  the  carbonates. 

Exp.  167. — Place  a  few  fragments  of  marble  in  a  flask,  and 
pour  upon  them  dilute  hydrochloric  acid.  The  gas  may  be  collected 
over  water  or  by  displacement.  (Use  apparatus  in  Fig.  20). 

CaO,  C02  +  2 HC1  =  CaCl2  +  H2O  +  CO2. 

300.  Physical    properties.     Carbonic    anhydride    is    a 
colorless,  coercible  gas,  having  a  peculiar,  pungent  odor. 
Its  specific  gravity  (1.529)   is  so  great   that   it   may   be 
poured  from  one  vessel  to  another  (Fig.  81)  ;  and,  con- 
sequently, its  rate  of  diffusion  is  so  small  that  it  some- 


172 


CHEMISTRY. 


FIG.  M. 


times  accumulates  in  wells  and  caverns.  This  is  notably 
seen  in  the  Grotto  dtjl  Cane,  near 
Naples. 

At  ordinary  temperatures,  car- 
bonic anhydride  is  condensed  by 
a  pressure  of  50  atmospheres  to 
a  colorless  liquid :  sp.  gr.  0.83. 
If  this  liquid  anhydride  is  lib- 
erated from  pressure,  a  portion 
rapidly  volatilizes,  and,  by  so 
doing,  produces  a  cold  of — 77° 
('..which  is  sufficient  to  freeze  the 
remaining  portion  into  a  snow- 
white,  flocculent  mass.  This  may  be  handled  notwith- 
standing its  low  temperature,  because  it 
is  kept  from  contact  with  the  hand  by 
a  layer  of  the  gas  (spheroidal  condition) ; 
but,  if  pressed  into  actual  contact  with 
the  skin,  it  produces  a  blister  like  a  burn. 
Wetted  with  ether,  it  easily  solidities  mer- 
cury, and  in  racuo  produces  a  cold  of  ^HHH^F 

-110°     C.  Kl«.  M. 

301.  Chemical  proper- 
ties. Carbonic  anhydride 
is  incombustible,  and  ex- 
tinguishes the  flame  of  or- 
dinary combustibles.  Its 
high  specific  gravity  and 
power  of  extinguishing 
flame  may  be  illustrated 
by  the  following  experi- 
ments. 

Exp.  168. — An  ordinary 
soap  bubble  will  float  on  the 
surface  of  the  gas.  Evolve  the  gas  in  a  broad-mouthed  jar  by 
.placing  marble  ohippings  and  acid  at  tbe  bottom.  (Fig.  82). 


FlG  j 


CARSOXIC  ACID. 


173 


Exp.  169.  —  Balance  a  light  paper  box  on  an  ami  of  a  balance: 
the  anhydride  may  be  poured  into  .the  box  and  will  depress  the 
beam.  (Fig.  83). 

Exp.  17O.—  A  lighted  taper  .plunged  into  the  gas  will  be 
extinguished.  It  may  also  be  extinguished  by  pouring  the  gas 
upon  it  from  some  distance  above.  (Fig.  81). 

Exp.  171.  —  The  gas  may  be  drawn  up  in  buckets  from  the 
bottom  of  large  jars  and  used  as  in  Exps.  1G9  and  170.  It  may 
be  reduced  to  carbonous  oxide  by  ignited  coals,  and  also  by  some 
metals,  as  Zn  and  Fe,  at  high  temperatures. 

Exp.  172.  —  Pass   a  dry  stream  of  the  gas  over  melted  sodium. 
It  is  in  part  reduced 
to  carbon,  while  an- 
other part  combines 
with     the     sodium. 
(Fig,  82). 
3C0 


2 

2(Na2O,  C0a)+  C. 
The  product  formed 
in  this  case  is  the 
normal  sodium  car- 
bonate, Na2COa. 


Potassium  hy- 
drate rapidly  absorbs  the  gas,  and  may  be  used  to 
separate  it  from  mixtures  with  most  other  gases.  When 
a  large  excess  of  the  gas  is  passed  into  a  solution  of 
potassium  hydrate,  the  product  formed  is  KIICO3,  acid 
potassium  carbonate,  or  bicarbonate  of  potassa.  Similar 
salts  are  formed  with  the  other  metals.  There  are  also 
sesquicarbonates  which  may  be  regarded  as  mixtures 
of  the  other  two,  as  2NaHCO3  -f  Na2CO3  ==  Na4H2, 
3CO3.  and  orthocarbonates  like  half-burned  lime,  2CaO, 
CO2  or  Ca"2C04. 

The  solution  of  the  gas  in  water  (§  36)  is  regarded 
as  carbonic  acid,  but  it  has  not  been  isolated.  Its  the- 
oretical formula  should  be  C/F(OH)4  or  H4CO4,  a  tetra- 
basic  ortho-acid.  Generally  speaking,  it  acts  as  a  di- 
basic acid,  having  the  formula  H2CO8  or  H2O,  CO2. 


174  CHEMISTRY. 

Carbonic  acid  is  a  feeble  acid  that  is  easily  displaced 
by  almost  all  other  acids.  All  the  carbonates,  except 
those  of  the  alkalies,  are  decomposed  by  heat.  These 
are  decomposed  when  boiled  with  calcium  hydrate. 

302.  Physiological   properties.     Carbonic    acid   is   not 
poisonous   when    taken    into    the    stomach,  but   the   gas 
acts   injuriously    when    breathed,    except    when    exceed- 
ingly  dilute.     Fatal    accidents    have    occurred  from  the 
accumulation    of  this   gas  in  old  cisterns,  brewers'  vats, 
and    in    mines,    where    it    is    known    by    the    name    of 
"  choke    damp."     Air    containing   one    per    cent   of  car- 
bonic anhydride  produces  in   most  persons  languor  and 
headache;    a  larger  proportion  causes  stupor;    and  nine 
per  cent  is  sufficient  to  cause  suffocation  and  death. 

The  air  expired  from  the  lungs  contains  about  four 
per  cent  of  the  gas.  Air  which  has  been  twice  respired 
contains  enough  of  the  gas  to  extinguish  a  taper.  A 
full-sized  man  evolves  from  his  lungs  and  skin  about 
0.7  cubic  foot  per  hour  of  carbonic  anhydride.  In  order 
that  he  may  continue  to  breathe  without  inconvenience, 
it  is  necessary  that  this  evolved  gas  should  be  distrib- 
uted through  at  least  140  cubic  feet  of  fresh  air,  so  that 
it  may  not  exceed  one-half  of  one  per  cent  of  the  air. 
Hence,  there  is  a  necessity  for  abundant  ventilation  of 
occupied  apartments.  It  should  be  remembered  that 
lamps  also  produce  carbonic  acid.  A  gas  burner  con- 
suming six  feet  of  gas  per  hour  evolves  as  much  car- 
bonic acid  as  one  man. 

303.  Uses.     Carbonic  anhydride   has   proved   of  great 
service  in  extinguishing  fires  in  coal  mines ;  and  several 
devices  have  been  proposed  by  which  it  may  be  turned 
to    account    in    extinguishing    ordinary    conflagrations. 
Water  containing  carbonic  acid   is  of  great  importance 
in  the  chemistry  of  Nature.     It  is  capable  of  dissolving 
calcium  carbonate  and  other  bodies  not  soluble  in  pure 

.water,  and  thus  assists  in  disintegrating  rocks  and  pre- 


CARBONIC  DISULPHIDE. 


175 


paring  soils  for  the  uses  of  plants.  The  gas  is  also 
used  in  manufacturing  various  carbonates,  as  those  of 
sodium  and  lead. 

304.  Tests.  Free  carbonic  anhydride  may  be  recog- 
nized by  passing  it  into  lime-water  (Fig.  5),  when  it 
causes  a  precipitate  of  calcium  carbonate. 

Exp.  173. — The  presence  of  this 
gas  in  expired  air  may  readily  be 
shown  by  blowing  a  deep  breath  into 
lime-water.  (Fig.  85). 

Exp.  174. — The  carbonic  anhy- 
dride in  air  may  be  shown  by  the 
following  apparatus.  A  wide  tube, 
a  foot  long,  is  placed  in  an  inclined 
position,  and  is  fitted  at  both  ends  FlG  85 

with  vertical  tubes.     It  is  then  half- 
filled  with  lime-water.    The  air  slowly  drawn  through  this  by  means 
of  an   aspirator  renders  the  lime-water  milky.     The  aspirator  may 
consist  of  a  large  can  furnished  with  a  siphon,  as  shown  in  Fig.  86. 

The  carbonates  are  known   by  their  effervescing  and 

by  evolving  CO2 
when  a  strong 
acid  is  poured 
upon  them. 

305.  Carbonic 
disulphide,  CS2,  is 

prepared  by  pass- 
ing the  vapor  of 
sulphur  over  coke 
or  charcoal  heated  to  redness.  It  is  frequently  present 
as  one  of  the  most  injurious  impurities  in  coal  gas. 

306.  Physical  properties,  Carbonic  disulphide  is  a 
colorless,  diathermanous  liquid  of  high  refracting  powers 
(1.645),  and,  when  pure,  of  not  unpleasant  odor :  sp.  gr. 
1.27.  Usually,  however,  the  odor  of  its  vapor  is  very 


FIG.  86. 


176  CHEMISTRY. 

offensive.    It  volatilizes  rapidly  at  ordinary  temperatures, 
producing  great  cold,  and  boils  at  4(>.G°  C. 

Exp.  175. — Place  a  watch-glass  filled  with  carbonic  disulphido 

on   a   glass  plate  covered  with  water,  and  evaporate    it    rapidly  by 

blowing  a  current  of  air  over  its  surface.  The  glass  will  be  frozen 
to  the  plate. 

It  has  never  been  solidified  by  cold.     Its  vapor  is  so 
inflammable  that  it  ma}'  be  ignited  by  a  glass  rod  heated 
below  redness  (Fig.  S7)  ;  consequently,  great 
care  should  be  used  in  experimenting  with  it. 

307.  Chemical  properties.  Carbonic  disul- 
phide  is  a  sulphur  acid,  capable  of  com- 
bining with  alkaline  sulphides  to  form 
sulphocarbonates,  as  K2S,  CS2.  It  is  easily 
decomposed  into  its  elements,  carbon  and 
sulphur,  and  hence  may  be  used  to  form 
various  carbon  and  sulphur  compounds. 

308.  Uses.     Carbonic  disulphide  is  an  excellent  solvent 
for   phosphorus,    iodine,    sulphur,   many  resins,  and  oils. 
It    is    very    extensively    used    in    the    extraction    of  fats 
and  oils,  and  in  the  cold  process    of  vulcanizing    caout- 
chouc.    The  poisonous  properties  of  its  vapor  have  been 
turned  to  account  for  killing  insects  in  grain. 

£}  O 

SILICON  OR  SILICIUM. 

309.  Silicon    is    always    found    in    combination    with 
oxygen,  either  alone  as  silicic  anhydride  (SiO2),  in  the 
form  of  quartz  or  sand,  or  united  with  various  metallic 
oxides,  forming  silicates. 

310.  Preparation.     Silicon  is  prepared  by  heating  dry 
potassium    silico-fluoride    with    potassium   or  aluminium. 

2  KF,  SiF4  -f-  K4  =  6  KF  +  Si. 

311.  Physical  properties.     Silicon  may  be  obtained  in 


SILICA.  177 

three  forms :  (1)  a  soft,  brown,  amorphous  powder ; 
(2)  as  hexagonal  plates,  which  resemble  graphite  in 
luster  and  power  of  conducting  electricity — sp.  gr.  2.5; 
and  (3)  in  iron-gray  needles  or  octahedra,  which  are  so 
hard  as  to  scratch  glass  like  the  diamond.  All  these 
forms  are  fusible  at  a  temperature  between  1600°  C. 
and  1800°  C. 

312.  Chemical    properties.     Amorphous    silicon    burns 
brilliantly  in  air  to  SiO2,  and  dissolves  in    hydrofluoric 
acid   to   SiF4.     The    other    forms    of  silicon    are   incom- 
bustible in  air,  and  are  insoluble  in  hydrofluoric  acid. 

Like  carbon,  silicon  is  found  in  cast  iron  and  in  cer- 
tain other  metals,  either  mixed  or  in  compounds  which 
resemble  alloys;  but,  unlike  carbon,  it  forms  but  one 
known  compound  with  hydrogen,  and  that  of  a  very 
unstable  character.  It  must,  however,  be  remarked  that 
numerous  alcohols  and  ethers  are  known  which  contain 
silicon  in  place  of  carbon. 

313.  Hydrogen  silicide,  H4Si,  is  prepared   by  decom- 
posing  magnesium    silicide    by  dilute  hydrochloric  acid. 
Mg2Si  +  4IICl:=H7Si-f  2MgCl2.     It  is  a  colorless  gas, 
insoluble  in  water  that  is  free  from  air. 

314.  Chemical  properties.     Pure    hydrogen    silicide   is 
not  spontaneously  inflammable  at  ordinary  temperatures, 
but  is  easily  decomposed  by  heat  into  amorphous  silicon 
and  hydrogen.     When    mixed  with   hydrogen,  it  ignites 
in  the  air  spontaneously,  evolving  silicic  anhydride,  and 
depositing  on  a  cold  surface  a  brown  film  of  silicon. 

315.  Silicic    anhydride,    or    silica,    Si02.     The    purest 
natural  variety  of  silica  is  quartz,  or  rock  crystal.    This 
is  found  in  beautiful,  six-sided  prisms,  terminated  by  six- 
sided  pyramids.     It   also   occurs   crystalline  very  nearly 
pure — as  amethyst,  rose  quartz,  and  Cairngorm  stones; 
and   in   the    amorphous   form — as  jasper,    agate,    onyx, 

Chem.— 12. 


178  CHEMISTRY, 

carnelian,  chalcedony,  and  flint.  The  opal  is  silica  com- 
bined with  water.  The  whiter  varieties  of  sand  are 
nearly  pure  silica ;  the  yellow  color  of  ordinary  sand 
and  sandstones  is  due  to  the  presence  of  an  oxide  of 


iron. 


316.  Preparation.     The    gelatinous    precipitate    which 
forms  when  silicon  fluoride   is  decomposed  by  water,  is 
a  compound  of  silicic  anhydride  and  water,  which  may 
be  regarded  as  silicic  acid.     If  this  is  washed  and  dried, 
the  white  powder  which  is  left  is  silicic  anhydride. 

317.  Physical  properties.     Quartz  is  so  hard  as  to  be 
able   to  scratch  glass:    sp.  gr.  2.5  to  2.9.     The  artificial 
silica   is   so   finely  divided  that  it  is  remarkable  for  its 
extreme  mobility,  the  slightest  breath  easily  blowing  it 
away.    All  varieties  of  silica  are  infusible  except  by  the 
extreme  heat  of  the  oxy-hydrogen  flame. 

318.  Chemical  properties.     Ignited  silicic  anhydride  is 
insoluble    in    all    acids    except    hydrofluoric.      It    unites 
with  the  alkalies,  either  on  boiling  with  their  solutions 
or   on    fusing   in   the    dry  state,  forming  silicates  which 
are   soluble   in  water.     These   compounds  are  known  as 
soluble  glass. 

319.  Silicic  acid.     If  a  solution  of  an  alkaline  silicate 
be  slightly  acidulated  with  hydrochloric  acid,  the  gelat- 
inous  precipitate  which    forms  is  probably 
2II2O,  SiO2  =  H4SiO4,   or   orthosilicic  acid. 
In  this  state  it  is  readily  soluble   either  in 
alkalies  or  in  hydrochloric  acid.    Silicic  acid 
soluble   in  water  may  also   be   obtained  by 
dialysis. 

Exp.  176. — Support  a  cone  of  parchment  paper 
in   a   vessel   filled  with   distilled  water,    so  that   the 
water  may  come  in  contact  with  the  outer  surface  of  the  cone,  and 
fill  the  cone  with  a  solution   of  silica   in    hydrochloric  acid.     In  a 


SILICATES.  179 

few  days  the  alkaline  chlorides  derived  from  the  soluble  glass  and 
the  hydrochloric  acid  will  dialyze  through  the  paper,  and  a  solution 
of  silicic  acid  in  water  remain  in  the  cone. 

This  solution  may  be  evaporated  in  vacuo  to  a  transparent  glass, 
which  is  metasilicic  acid,  H2O,  SiO2  =  H2SiO3.  The  solution  has 
a  great  tendency  to  assume  the  gelatinous  form,  and  can  not  be 
preserved. 

Many  thermal  springs  also  contain  silica  in  solution. 
The  Geysers  of  Iceland  contain  considerable  quantities, 
and,  as  the  liquid  cools,  deposit  the  silica  upon  objects 
exposed  in  their  basins.  In  these  cases  we  must  sup- 
pose the  solvent  power  to  be  due  to  the  presence  of 
alkaline  carbonates,  assisted  by  the  high  temperature. 
Silica  dissolved  in  soil  is  taken  up  by  plants;  notably 
so  by  the  cereals,  grapes,  and  rushes.  It  forms  beauti- 
ful crystals  in  the  leaves  of  the  Deutzia  scabra. 

320.  The   natural    silicates    arc   very    numerous,    and 
are  often  of  a  very  complex  nature.     Among  these  are 
clay  and  kaolin  (A12O3,  2SiO2),  potash  mica  (A16K2O10, 
6SiO2),  common  mica  (Mg4Af2O7,  2  SiO2),  garnet  (Ca3 
A12O6,   3SiO2),     the     feldspars,     orthoclase     (K2A12O4, 
6SiO2),    and    albite    (Na2Al2O4,    6  SiO2).      Talc,    meer- 
schaum, serpentine,  and  hornblende  are  principally  sili- 
cates of  magnesia. 

321.  Of  the  artificial  silicates,  only  those  of  the  alka- 
lies are  soluble  in  water.     These  are  largely  used,  under 
the  name  of  soluble  glass:    (1)  in  mural  paintings;   (2) 
for  the  preservation  of  building  stone ;  (3)  for  cleansing 
wools;    and    (4)    in    preparing    mordanted    calicoes'  for 
dyeing. 

Glass  is  a  mixture  of  an  alkaline  silicate  with  one  or 
more  insoluble  silicates.  Glass  is  made  by  fusing  silica 
with  potash  or  soda  and  some  base  which  is  calculated 
to  render  the  mixture  less  soluble,  more  infusible,  or 
more  transparent.  Crown  glass  is  a  silicate  of  potash 
and  lime;  flint  glass  is  a  silicate  of  potash  and  lead; 


180  CHEMISTRY. 

ordinary  window  glass  is  a  silicate  of  soda  and  lime. 
The  cheaper  forms  of  glass  generally  contain  also  sili- 
cates of  alumina  and  of  iron.  Ferrous  oxide  imparts  a 
green  color  to  glass,  but  ferric  oxide  gives  only  a  yel- 
lowish tinge.  Hence,  the  green  color  due  to  iron  may 
be  prevented  by  the  addition  of  some  oxidizing  agent, 
as  arsenious  acid  or  niter.  Manganese  dioxide  imparts 
a  purple  color  to  glass.  If  green  and  purple  glasses  are 
fused  together,  a  colorless  glass  results.  We  may  sup- 
pose this  effect  to  be  produced  either  by  reason  that 
the  two  colors  are  complementary  to  each  other,  or  that 
the  manganese  acts  as  an  oxidizing  agent.  Colored 
glass  is  produced  by  small  quantities  of  various  sub- 
stances :— red,  by  cuprous  oxide ;  ruby,  by  gold  ;  yellow, 
by  antimony;  blue,  by  cobalt;  white  enamel,  by  stannic 
oxide.  The  glass  used  for  imitation  of  precious  stones 
contains  generally  a  large  proportion  of  lead  oxide,  also 
frequently  baryta  and  boracic  acid. 

TESTS. — Silica  may  be  recognized,  (1)  by  its  insolubility  in  acids; 
(2)  by  its  infusibility  before  the  blowpipe.  (3)  Make  a  bead  of 
microcosmic  salt  (NaNH4HPO4)  on  a  loop  of  platinum  wire,  and 
add  a  trace  of  a  silicate.  On  again  fusing  the  bead,  the  silica  will 
remain  undissolved1  and  will  float  as  a  spongy  mass  (silica  skeleton) 
in  the  molten  bead.  An  excess  of  silica  renders  the  bead  opaque. 


TIN. 

322.  The  only  important   ore  of  tin  is  cassiterite,  or 
tin  stone,  SnO2.    This  is  found  mixed  with  other  metal- 
lic ores  in  veins  traversing  the  primitive  rocks,  and  also, 
in  a  purer  condition,  as  stream  tin  ore,  in  the   alluvial 
deposits  which  are  formed  by  the  natural  disintegration 
of  these  rocks.     The  largest  supplies  of  tin  are  obtained 
from  Cornwall,  Malacca.  Banca,  and  Australia. 

323,  Preparation.     Tin    is    obtained    by    smelting    the 
ore  mixed  with  pulverized  anthracite  or  charcoal. 


TIN.  181 

324.  Physical  properties,     Tin  is  a  soft,  white  metal: 
sp.  gr.  7.29.     It  fuses  at   228°  C.,  but  is  not  easily  vol- 
atilized.    Its  tenacity  and  ductility  are  very  low,  but  it 
is  highly  malleable,  as  is  shown  in  the  manufacture  of 
tin  foil.     It  exhibits  a  considerable  tendency  to  crystal- 
lize.    A  bar  of  tin,  when  bent,  emits  a  peculiar,  creaking 
sound,  which   is   probably  due   to   the   interior   crystals 
breaking  against  each  other. 

Exp.  177.— Wash  the  surface  of  tin  plate  with  warm,  dilute 
nitro-hydrochloric  acid.  In  a  little  while,  a  mass  of  crystalline 
forms  will  appear  (moiree  metallique}. 

325.  Chemical  properties.     Tin  unites  readily  with  sul- 
phur,   chlorine,   phosphorus,   and   oxygen,  when    heated 
with  these   elements.     It   retains   its   luster   for   a   long 
time,  even  in  the  presence  of  moist  air ;  but,  when  fused 
in  air,  rapidly  oxidizes   to   white    stannic   oxide,    SnO2. 
It   forms   two    series   of  compounds :    the    stannous,    in 
which   it   is   bivalent,   and  the   stannic,   in   which   it   is 
quadrivalent. 

326.  Uses.     Tin   is  generally  employed  in  alloys  and 
as   a   coating   for   other  metals.     Tin  plate  is  simply  a 
sheet  of  iron  covered  with  tin.     It  is  made  by  carefully 
cleansing   iron    plates   from    every   trace    of  oxide,    and 
then  immersing  them  in  melted  tin.    A  cheaper  variety, 
terne  plate,  is   coated  with    an    alloy   of  tin    and    lead. 
Brass    pins    are    coated    with    tin    by    boiling    them    in 
water  containing  granulated  tin,  acid  potassium  tartrate, 
alum,  and  common  salt. 

Among  the  alloys  of  tin  are  solder  and  pewter  (Sn 
-f-  Pb),  Britannia  metal  (Sn  -f  Cu  -f-  Sb),  gun  metal, 
bronze,  and  bell  metal  (Cu  -f-  Sn).  The  silvering  ap- 
plied to  the  backs  of  mirrors  is  tin  foil  amalgamated 
with  mercury. 

327.  Stannous   chloride,  SnCl2,2H2O,   is   obtained   in 
prismatic  needles  by  dissolving  tin  in  hydrochloric  acid. 


182  CHEMISTRY. 

It  has  a  strong  attraction  both  for  chlorine  and  oxygen, 
and  hence  acts  as  a  powerful  reducing  agent. 

Exp.  178. —  Add  to  a  solution  of  HgCl.,  a  drop  or  two  of 
SnCl2:  calomel  will  bo  fornu-d.  2IIgC.M2-f  SnCl2=Hg^Cl2-f  SnCl4. 
Now  add  the  SnCl2  in  excess:  the  pivt-ipitate  is  dark  gray,  metallic 
mercury.  Hg2Cl2  +  SnCl2  =  2_Hg  +  SnCl4. 

Stannous  chloride  is  converted  by  water  into  an  in- 
soluble oxychloride  (Sn2C'l2O).  This  change  may  be 
prevented  by  the  addition  of  either  hydrochloric  or  tar- 
taric  acid.  It  is  used  by  the  dyer  as  a  deoxidizing 
agent,  under  the  name  of  ••  tin  salt." 

328.  Stannic    chloride,   SnfM4,   may   be   obtained   as  a 
heavy,  fuming  liquid  by  heating  tin   tilings  in  dry  chlo- 
rine gas.     It  readily  combines  with  a   small  quantity  of 
water    to    form    Sn(M4.  f>  II2O ;    but    an    excess    of  water 
decomposes    it.     A    solution    of  this    chloride    is    readily 
prepared  by  dissolving  tin  in  hydrochloric  acid,  to  which 
a  very  little  nitric  acid   has  been  added. 

Stannic  chloride  forms  double  salts  with  the  chlorides 
of  the  alkalies.  The  "pink  salt,"  used  by  dyers  in  the 
production  of  red  colors,  is  2NH4C1,  Sn(Jl4. 

329.  Stannous    oxide    is    formed    as   a    white    hydrate, 
2SnO,  H2O,  by  precipitating  stannous  chloride  with  so- 
dium carbonate.     On  boiling  this  mixture,  the  anhydrous 
oxide,  SnO,  forms  as  a  brown  powder. 

It  is  a  weak  base  which  dissolves  in  acids  to  form 
stannous  salts.  The  moist  hydrate  readily  absorbs  oxy- 
gen and  becomes  stannic  oxide.  Caustic  potash  converts 
it  into  metallic  tin  and  stannic  oxide,  which  combines 
with  the  potash. 

330.  Stannic  oxide,  SnO2,  is  formed  when  tin  is  fused 
in  contact  with  the  air,  or  when  either  of  the  hydrates 
are  strongly  ignited.     It  is  a  white  powder  so  hard  that 


STANNIC  SALTS.  183 

it  is  used  for  polishing,  under  the  name  of  "  putty 
powder."  It  is  insoluble  in  acids,  but,  when  fused  with 
the  alkalies,  forms  soluble  compounds  which  are  called 
stan  nates. 

Sodium  stannate,  Na2O,  $nO2  =  Na2SnO3,  is  used  as 
a  mordant  by  calico  printers.  If  a  solution  of  this  salt 
in  water  be  acidulated  with  hydrochloric  acid,  a  white, 
gelatinous  precipitate  falls;  this  is  II2O,  SnO2.  As  it 
readily  combines  with  metallic  oxides,  it  is  stannic  acid; 
but  it  also  dissolves  in  the  stronger  acids,  and  forms 
with  them  stannic  salts,  in  which  it  plays  the  role  of  a 
weak  base. 

Metastannic  acid,  5H2O,  5SnO2  =  Sn5H10O1 5,  is  formed 
by  the  action  of  nitric  acid  upon  metallic  tin.  It  is  en- 
tirely insoluble  in  acids,  but  forms  soluble  metaatannates 
with  the  alkalies. 

331.  Stannous  sulphide,  SnS,  precipitates  as   a   brown 
hydrate  when   hydrogen  sulphide  is  passed  into  a  solu- 
tion of  a  stannous  salt.     When  treated  with  the  alkaline 
persulphides,  it  becomes  SnS2. 

This  stannic  sulphide  is  also  produced  as  a  dull  yellow  hydrate 
when  hydrogen  sulphide  is  passed  into  solutions  of  stannic  salts. 
It  is  sulphostannic  acid,  and  dissolves  easily  in  alkaline  sulphides. 

Stannic  sulphide  may  also  be  produced  in  the  dry  way  by  care- 
fully heating  tin  amalgam  with  sulphur  and  sal-ammoniac  in  a 
Florence  flask.  Beautiful  yellow,  scales  are  left  in  the  flask,  which 
are  called  mosaic  gold,  and  are  used  for  decorative  purposes. 

332.  Tests.     The   reactions   mentioned   in  speaking  of 
the   preparation    of  the    hydrated   oxides  and  sulphides 
are  tests  for  the  salts  of  tin.     Stannous  chloride  is  dis- 
tinguished from  stannic  chloride  by  its  reducing  action 
on  mercuric  chloride;  and  by  its  giving,  with  an  excess 
of  auric  chloride,  a  precipitate,  u  the  purple  of  Cassius  " 
(AuSnO2?).     All  tin  compounds,  when  heated   on   char- 
coal with   sodium   carbonate,   yield   a   malleable  globule 
of  tin. 


184  CHEMISTRY. 

333.  Titanium  and  zirconium  arc  rare  tetrad  elements. 
Titanium  occurs  in  nature  as  titanic  anhydride,  TiO2 
(Rutile),  but  more  frequently  in  iron  ores  as  a  titanate 
of  iron.  The  slags  obtained  in  smelting  such  ores  with 
charcoal  frequently  contain  copper-colored  crystals  which 
have  the  probable  formula  Ti(CN)23.Ti8N2.  These  are 
interesting,  because  they  show  the  direct  union  of  at- 
mospheric nitrogen  with  titanium  and  carbon.  When 
titanic  anhydride  is  strongly  heated  in  ammonia,  it  also 
forms  TiX2  (titanium  nitride). 

Zirconium  has  three  allotropic  states  resembling  those 
of  silicium.  Its  principal  oxide,  ZrO2  (zirconia),  acts 
both  as  a  base  and  as  an  acid.  The  sulphates  of  zir- 
conium and  of  titanium  are  decomposed  by  a  large 
excess  of  water. 


Recapitulation. 

These  elements  are  grouped  together  because  they  act  as  tetrads, 
forming  tetrachlorides  (RC14)  and  acid  anhydrides  (RO^), 
which  form  soluble  salts  with  the  fixed  alkalies. 

They  may  be  divided  into  two  sub-groups: 

(a)  Carbon,  silicon. 

(b)  Titanium,   zirconium,  tin. 

Carbon  and  silicon  are  non-metals  which  are  remarkable  for  not 
conforming  to  the  law  of  the  specific  heat  of  atoms  (p.  55). 
Their  compounds  are  very  numerous  and  are  of  similar  con- 
stitution. 

The  second  sub-group  consists  of  semi-metals,  tin  being  popularly 
classed  as  a  metal  on  account  of  its  physical  properties.  Their 
compounds  strongly  resemble  those  of  silicon. 

Several  of  these  elements  form  dyad  compounds;    as,  CO,  SnCl2. 


CHAPTBK   X. 

THE    ELECTRO-POSITIVE    ELEMENTS. 

334.  The   metals  are  distinguished  from  the  elements 
previously    studied    principally    in    the    fact    that    their 
oxygen  compounds  are  generally  basic.    The  semi-metals 
closely   agree  with    them   in   their   physical   properties ; 
and  for  this  reason  arsenic,  antimony,  bismuth,  and  tin 
will,  in  this  chapter,  be  again  grouped  with  the  metals. 
They  form   undoubted   alloys  with    the   metals,   and,  as 
already  stated,  are  a  connecting  link  between  the  non- 
metals  and  the  metals. 

Physical  Properties  of  Metals. 

335.  (I)   Great   opacity.     Some  metals,  when  in  very 
thin  sheets,  are  translucent.     Thus,  gold    leaf  transmits 
light  of  a  green  color. 

336.  (II)   Luster.     When   the  metals  are  very  finely 
divided,   as    iron    reduced   by  hydrogen  (Exp.  30),  they 
are  generally  dull  looking  powders;  but  when  they  are 
melted    or   beaten    into    a    compact  mass,  they  have   in 
a  high  degree  the  power  of  reflecting  light,  which  gives 
them  the  so-called  metallic  luster. 

Exp.  179. — Add  ferrous  sulphate  to  gold  chloride.  Brown, 
metallic  gold  precipitates.  On  rubbing  this,  when  dry,  with  a  hard, 
smooth  substance,  it  assumes  the  yellow  luster  of  gold. 

The  natural  luster  of  silver  and  of  gold  is  very  great. 
Metals  which  are  hard  enough  to  be  polished,  like  iron 
in  the  form  of  steel,  give  splendid  reflecting  surfaces. 

(185) 


186  CHEMISTRY. 

The  mirrors  or  specula  of  the  ancients  were  made  of 
metals.  An  alloy  of  tin  and  copper  is  still  used  for  this 
purpose  in  reflecting-  telescopes. 

337.  (HI)  The  color  of  most  of  the  metals  is  white  or 
gray.     Silver,  tin,  and    sodium    are    almost    pure    white; 
iron,    somewhat   gray;    lead    and    zinc,    bluish;    calcium, 
pale   yellow;    gold,  full    yellow;    bismuth,    reddish;    and 
copper,  a  full  red. 

338.  (IV)   A  few  metals  yield  a  peculiar  odor  when 
rubbed,  as    is   the  case  with    copper   and    tin.     Many  of 
their  salts  have  an  acrid  histe  which   is   called   metallic. 
To  the  formation  of  these  salts  is  due  the  peculiar  taste 
observed  when  a  tarnished  piece  of  copper    or   brass   is 
placed  on  the  tongue. 

339.  (V)  Crystallization.     Many  metals   may  be   crys- 
tallized  in    some   form    of  the    isometric    system,    as    the 
cube,  octahedron,  etc.     The    metals   most   easily  crystal- 
lized   are   generally   the   brittle    metals,   as   bismuth    and 
antimony. 

Exp.  180. — Melt  several  pounds  of  lead  in  a  crucible  and  set 
it  aside  to  cool.  As  soon  as  a  crust  has  formed  on  the  top,  pour 
out  the  still  molten  interior,  and  a  mass  of  interlaced  octahedra 
will  remain. 

Exp.  181. — Suspend  n,  bright  strip  of  zinc  in  a  dilute  solution 
of  lead  acetate.  After  a  few  days,  arborescent  crystals  of  lead  will 
be  formed  (arbor  Saturn!). 

Some  metals  while  in  the  solid  state  tend  to  assume 
a  crystalline  structure  under  the  influence  of  repeated 
blows.  The  sudden  breaking  down  of  iron  bridges  and 
of  iron  axles  in  railway  cars  has  been  attributed  to  this 

cause. 

340.  (YT)   The  cohesion  of  metals  varies  greatly.     At 
ordinary    temperatures,    mercury    is    a    liquid;    all    the 


PHYSICAL  PROPERTIES  OF  METALS. 


187 


others  are  solids.  Some  of  these,  as  sodium  and  potas- 
sium, are  so  soft  that  they  may  be  kneaded  like  wax; 
others,  as  chromium  and  manganese,  rival  the  diamond 
in  hardness. 

The  soft  metals  and  the  brittle  metals  have  generally 
little  tenacity :  lead  and  zinc  are  examples.  A  bar  of 
steel  one  square  inch  in  section  has  resisted  a  stretching 
force  of  nearly  180,000  pounds.  Copper  wire  has  about 
one-third  of  this  tenacity. 

341.  (VII)  Many  metals  are  malleable;  that  is,  they 
are  capable  of  being  flattened  out  under  the  hammer 
or  between  rollers;  and  are  also  ductile,  or  capable  of 
being  drawn  into  fine  wires.  The  following  table,  which 
gives  the  relative  tenacity,  ductility,  and  malleability, 
shows  that  the  metals  do  not  possess  these  properties 
in  equal  degrees. 


RANK. 

TKNACITY. 

DUCTILITY. 

MALLEI 

rXDKR  THK 
HAMMKK. 

BILITY 
BKT  WKKX 
ROLLKKS. 

1 

Iron 

Platinum 

Lead 

Gold 

2 

4 

5 

Copper 
Platinum 
Silver 
Zinc 

Silver 
Iron 
Copper 
Gold 

Tin 

Gold 
Zinc 
Silver 

Silver 
Copper 
Tin 
Lead 

G 

7 

Gold 
Lead 

Zinc 
Tin 

Copper 
Platinum 

Zinc 
Platinum 

8 

Tin 

Lead 

Iron 

Iron 

The  ductility  and  malleability  are  increased,  within 
certain  limits,  by  a  high  temperature.  Iron  is  rolled 
when  at  a  white  heat;  zinc  is  most  malleable  when 
between  105°  C.  and  150°  C. 

342,  (VIII)  All  the  metals  are  fusible,  Mercury, 
cadmium,  zinc,  magnesium,  potassium,  sodium,  and  ru- 
bidium are  so  readily  vaporized  that  they  may  be  puri- 


188 


CHEMISTRY. 


fied    by    distillation.     Others    of  the    metals    have    been 
volatilized,  but  only  at  high  temperatures. 

343.  (IX)  The  specific  gravity  of  these  elements  ex- 
hibits a  wonderful  difference.  Some  are  lighter  than 
water.  The  common  metals  are  from  seven  to  nine 
times  heavier  than  water  (lead,  11.33).  The  noble  metals 
are  the  heaviest  bodies  known. 

The  following  table  exhibits  the  specific  gravities  and 
fusing  points  of  the  metals.* 


KLKMKXT. 

OKA  VII 

Lithium 

.59 

Potassium 

.80 

Sodium 

.97 

Rubidium 

1.52 

Calcium 

1.58 

Magnesium 

1.74 

Glucinum 

2.10 

Strontium 

2.54 

Aluminium 

2.56 

Barium 

4. 

Arsenic 

5.03 

Gallium 

5.'.) 

Antimony 

6.72 

Chromium 

7.01 

Zinc 

7.13 

Indium 

7.42 

Tin 

7.30 

Iron 

7.84 

Manganese 

8.02 

FTSINU 
POINT. 

ELEMENT. 

SPECIFIC 
GRAVITY. 

FUSING 
POINT. 

180°  C. 

Cadmium 

8.56 

320° 

62°.5 

Molybdenum  s.i;:j 

1900°?  C. 

95°.6 

Nickel 

8.82 

1800°? 

38°.5 

Copper 
Cobalt 

8.94 
8.51 

1200° 
1800°? 

433° 

Bismuth 

9.8 

270° 

1000°? 

Silver 

10.57 

1023° 

Lead 

11.33 

332° 

700°? 

Ruthenium 

11.4 

2000°? 

450° 

Palladium 

11.8 

1900°? 

Thallium 

11.9 

290° 

-{-30° 

Rhodium 

12.1 

2000°? 

450° 

Mercury 

13.6 

—  39°.4 

1900°? 

Tungsten 

18.3 

1900°? 

433° 

Uranium 

18.4 

176° 

Gold 

19.20 

1250° 

2-28° 

Indium 

21.15 

2000°? 

1800° 

Osmium 

22.47 

2000°? 

1800°? 

Platinum 

21.5 

2000° 

344.  Natural  history.  Few  of  the  metals  are  found 
native.  Among  these  are  bismuth,  gold,  and  platinum, 
which  are  almost  always  found  in  the  state  of  metals; 
silver,  mercury,  and  copper,  which  are  found  native  less 
frequently;  arsenic  and  antimony,  which  are  seldom 
found  uncombined  with  the  other  elements. 


Temperatures  above  1000°  given  iu  this  table  are  only  approximate. 


CHEMICAL  PROPERTIES  OF  METALS.  189 

Generally  the  metals  occur  as  constituents  of  various 
minerals  and  ores.  Lead,  mercury,  copper,  zinc,  and 
iron  are  frequently  found  united  with  sulphur.  These 
sulphides  often  exhibit  a  brilliant  luster,  but  have 
neither  the  ductility  nor  the  tenacity  of  the  metals. 
Tin,  iron,  and  manganese  are  generally  found  as  oxides. 
Calcium  and  sodium  are  sometimes  met  with  as  flu- 
orides ;  and  there  are  also  chlorides  of  sodium  and  of 
potassium  in  enormous  quantities. 

Most  of  the  minerals  which  constitute  the  solid  crust 
of  the  globe  are  compounds  of  silica,  alumina,  lime,  and 
magnesia.  Thus,  ordinary  clay  is  mainly  aluminium 
silicate;  limestone  is  calcium  carbonate;  gypsum  is  cal- 
cium sulphate ;  the  micas  and  feldspars  are  compounds 
of  silica  and  alumina  with  other  silicates  of  soda,  potash, 
or  lime;  talc  and  serpentine  are  compounds  of  silica  and 
magnesia.  On  the  other  hand,  most  of  the  ores  which 
yield  the  metals  that  are  useful  in  the  arts  seldom 
occur  in  large  masses,  but  are  collected  in  compara- 
tively thin  beds,  or  seams,  called  mineral  veins. 

345.  Chemical  properties.  The  metals  exhibit  strong 
affinities  for  the  non-metals,  and  easily  form  stable  com- 
pounds with  them.  Such,  for  example,  are  the  binary 
compounds  with  oxygen,  sulphur,  and  chlorine;  as, 
Fe203,  FeS2,  NaCl. 

More  commonly,  ternary  compounds  are  formed;  as, 
for  example,  the  hydrates  of  the  alkalies,  KHO,  NaHO. 
The  oxygen  compounds,  whether  anhydrides  or  hydrates, 
are  very  generally  basic.  The  protoxides  are,  almost 
without  exception,  strong  bases;  the  strongest  bases 
being  those  of  the  more  electro-positive  elements,  as 
K,  Na.  The  sesquioxides  are  generally  weak  bases,  and 
in  some  cases  may  act  as  acids. 

For  example,  A1203,  aluminium  sesquioxide,  easily  dissolves  in 
sulphuric  acid  to  form  aluminic  sulphate,  A12O3,  3SO3,  in  which 
it  plays  the  part  of  a  base.  It  also  dissolves  easily  in  a  solution 


190  CHEMISTRY. 

of  potassium    hydrate    to   form   K2O,  A12O3,  potassium    aluminate, 
in  which  it  plays  the  part  of  an  acid. 

The  higher  oxides  of  the  metals  are  sometimes  indif- 
ferent bodies,  as  MnO2,  PbO2  ;  or,  when  their  highest 
stage  of  oxidation  is  reached,  acid  anhydrides,  such  as 
CrO8,  MiiO8,  Mn,O7. 

o  o  «         i 

346.  If  a   metal   or  its  oxide  is  dissolved  in  an  acid, 
a  salt  is  formed.     The    acid    loses   the   whole   or   a    part 
of  its  hydrogen,  which  is  replaced  by  the  metal. 

The  halogen  compounds  of  the  metals,  as  NuCl,  CuCl2, 
arc  for  the  most  part  stable  salts,  not  decomposed  by 
water. 

The  ternary  salts  commonly  contain  a  metal  and  a 
non-metal,  or  an  acid  radical,  united  by  oxygen.  Prac- 
tically speaking,  it  makes  but  little  difference  what  for- 
mula is  assigned  to  these  salts,  if  it  correctly  represents 
the  percentage  composition.  The  tendency  among  chem- 
ists is  to  use  only  the  molecular  formula1*. 

347.  Almost  every  metal   has  a  long   series   of  salts, 
as   the   carbonates,   sulphates,   nitrates,    phosphates,    etc. 
Not  unfrequently  each  element   has,  besides  the  normal 
salt,  others  which  are  either  basic  or  acid  salts. 

Besides  these,  we  have  a  very  interesting  class  of  double  salts. 
These  very  generally  contain  one  kind  of  acid,  but  two  or  more 
bases,  as  K2Mg,  2SO4  -f  6H2O,  and  KA1,  2SO4  -f  12H2O.  A  com- 
plete description  of  all  these  compounds  would  require  many  vol- 
umes of  this  size;  hence,  we  shall  attempt  to  give  only  the  most 
important. 

348.  The  metals,   when  melted  together,   form  alloys. 
Such    are    brass   (Cu   and   Zn),   bell    metal,    and    bronze 
(Cu  and  Sn).     These  alloys  seem  sometimes  to  be  true 
chemical   compounds;    but.  for  the  most  part,  are  to  be 
regarded    as    solidified    mixtures    containing,   perhaps,   a 
true  compound  with  an  excess  of  one  of  the  ingredients. 

The    alloys    of  mercury    with    the    other    metals    are 


CLASSIFICATION  OF  THE  ELEMENTS.  191 

called  amalgams.     The  metallic  surface  of  ordinary  mir- 
rors is  an  amalgam  of  mercury  and  tin. 

349.  Classification.  The  table  on  the  following  page, 
prepared  by  Mendelejeff,  exhibits  a  very  ingenious  classi- 
fication of  all  the  elements.  They  are  arranged  in  lines 
in  accordance  with  their  atomic  weights:*  the  series, 
from  left  to  right;  the  groups,  from  top  to  bottom.  By 
this  arrangement,  elements  which  are  similar  in  proper- 
ties are  brought  in  close  juxtaposition ;  and  thus  those 
that  show  a  marked  gradation  of  properties  are  collected 
in  natural  groups.  Some  of  these  groups  have  been  long 
recognized,  as  the  chlorine  group  (7),  the  nitrogen  group 
(5),  the  carbon  group  (4),  which  we  have  already  studied. 
There  are  also  natural  groups  among  the  metals,  not  less 
marked.  Among  these  are  the  alkali  group  (1),  the 
alkaline  earths  (2),  the  earths  (3),  which  have  so  many 
points  of  resemblance  that  we  might  profitably  consider 
each  group  as  a  whole  before  proceeding  to  the  ele- 
ments which  compose  it.  Nevertheless,  the  grouping 
used  in  this  book  has  been  made  rather  for  the  conve- 
nience of  the  student  than  for  the  sake  of  any  theory, 
however  interesting  and  ingenious. 

Recapitulation. 

The  metals  differ  from  the  non-metals  in  their  physical  properties; 
such  as,  opacity,  luster,  color,  crystalline  form,  cohesion,  tenacity, 
malleability,  fusibility,  specific  gravity,  etc.  They  also  differ 
in  their  chemical  properties,  their  lower  compounds  with  O  and 
S  being  generally  basic.  Some  are  found  native,  but  generally 
as  ores,  containing  O,  S,  and  Cl;  or  as  salts,  containing  CO2 
and  SiO2. 

The  compounds  of  the  metals  with  each  other  are  called  alloys  or 
amalgams. 

All  the  elements  may  be  so  grouped  as  to  show  a  natural  gradation 
of  properties. 

*  Mendelejeff's  atomic  weights  are  frequently  different  from  those  on  pp.  12 
and  13,  59,  and  60. 


192 


CHEMISTRY. 


GO 


^ 


•S3IH3S 


CHAPTER    XI. 

THE    ALKALI    METALS. 


EIGHT. 

H 

p 

H 

ELEMENT. 

1 

O 

O 

E 

H 

? 

DISCOVERER. 

* 

I 

£ 
81 

g 

Lithium 

Li 

7 

0.578 

180° 

Arfwedson,  1817. 

Sodium 

Na 

23 

0.97 

95°.6 

Davy,            1807. 

Potassium 

K 

39.1 

0.865 

62°.5 

Davy,            1807. 

Rubidium 

Rb 

85.4 

1.52 

38°.5 

Bunsen,         1860. 

Caesium 

Cs 

133 

1.88 

26°.5 

Bunsen,         1860. 

Ammonium  |NH4|    18 

Silver 

Ag 

108 

10.57 

1023° 

350.  The  metals  of  this  group  are  all  monads,  forming 
but  one  chloride,  RC1.     The  first  five  —  lithium,  sodium, 
potassium,  rubidium,  and  caesium  —  are  the  alkali  metals. 
The  salts  of  the  hypothetical  ammonium  are  very  like 
those  of  potassium,  and  hence  it  is  convenient  to  study 
them  a't  this  place.     Silver   is   not  an  alkali  metal,  but 
may  be  reckoned  as  a  sub-group.     Some  of  its  salts  ,are 
isomorphous  with  those  of  sodium. 

351.  The   alkali   metals  have  the  following  properties 
in  common:    (1)   They  may  be   obtained   by   the   elec- 
trolysis of  their  fused  chlorides. 

(2)   They  are   soft,  light,  easily  fusible   metals  which 
volatilize  at  high  temperatures. 

Chem.-lS.  (193) 


194  CHEMISTRY. 

(3)  When   freshly  cut,  they  possess  a  strong  metallic 
luster;  but,  when  exposed  to  the  air,  they  soon  tarnish 
and    form    white    oxides    of   the    formula    R2O-     Their 
affinity  for  oxygen   increases  with    their   atomic  weight. 
When  caesium  is  set  free  by  electrolysis,  it  takes  fire  as 
soon  as  it  is  exposed  to  the  air;    and  hence  it  has  not 
as  yet  been  obtained  except  as  an  amalgam. 

(4)  Owing   to    their    strong   affinity  for  oxygen,  these 
metals  decompose  water  at  all  temperatures,  setting  free 
its  hydrogen.     The  oxides  thus  formed    dissolve    in   the 
excess   of  water   to   form  hydrates  of  the  formula  E2O, 
H2O    or    RHO.     These    hydrates    can    not    be    deprived 
of  their  water  by  heat  alone. 

(5)  The    alkaline    hydrates    are    the    strongest    bases 
known,  completely  neutralizing  every  acid.    They  change 
infusions  of  red  cabbage  or  violets  to  green ;  turmeric,  to 
brown ;  and  restore  litmus,  which  has  been  reddened  by 
acids,    to   blue.     In    a    concentrated    form    they   destroy 
animal    and    vegetable    tissue,    acting    u  caustic."     Their 
taste  is  acrid  and  unpleasant. 

(6)  AVhen  these  hydrates  are  exposed  to  the  air  they 
form  white  carbonates.     These   alkaline   carbonates   can 
not  be  decomposed  by  heat  alone.     They  are  all  soluble 
in  water    (lithium  somewhat  sparingly),  and  their  solu- 
tions react  alkaline  to  test  papers. 

(7)  All   these   elements   are   very  widely   diffused,  al- 
though none  of  them  are  found  native.    Their  chlorides 
are   found    in    very  many  mineral  springs,  and  are  fre- 
quently  associated    together.     They   are    also    found    in 
the    ashes    of    many    plants,    and    not    unfrequently    in 
minerals.    Nevertheless,  only  sodium  and  potassium  are 
found  in  large  quantities. 

SODIUM. 

352.  Sodium,  Na,  is  the  most  abundant  of  the   alkali 
metals.     It  is  distributed   very  widely.     As   a   chloride 


SODIUM.  195 

£N"aCl),  it  is  found  in  the  sea  water,  in  salt  springs, 
and  in  both  vegetables  and  animals.  It  is  also  found 
in  many  minerals,  as  rock  salt,  Chili  saltpeter  (NaNO3), 
and  some  silicates. 

353.  The  metal  was  first  prepared  by  Davy,  in  1807, 
by  electrolysis.     It    is    now    prepared    on    a  large   scale 
by  heating  an  intimate  mixture  of  dry  sodium  carbonate 
with    charcoal    to    a   white    heat:    Na0CO3  -j-  2C  =  Na2 
+  SCO.     At    this    temperature    the    carbon   reduces   the 
sodium,  which  distills  over  and  is  collected  under  petro- 
leum.    It    is   then   purified    by   remelting  under  a  thin 
layer  of  petroleum,  and  is  cast  into  bars. 

354.  Physical    properties.      Sodium    is    a    silver-white 
metal,  with  a  brilliant  luster  when  freshly  cut,  soft  like 
wax,    and    easily    moulded    by    the    hand.     Its    specific 
gravity  is  a  trifle  less  than  that   of  water.     It  oxidizes 
rapidly  even  in  dry  air,  and  must  be  kept  under  petro- 
leum.   "When  thrown  upon  water,  it  decomposes  it  read- 
ily ;    but   the    heat  evolved  is  not  generally  sufficient  to 
enkindle  the  hydrogen  set  free. 

Exp.  182. — Place  a  bit  of  filter  paper  on  the  surface  of  the 
water,  and  upon  it  a  pellet  of  sodium.  The  sodium  will  be  pre- 
vented from  rotation,  and  will  oxidize  so  rapidly  as  to  ignite  the 
hydrogen.  The  yellow  color  of  the  flame  is  due  to  the  sodium 
vapor  which  is  simultaneously  burned.  The  water  contains  sodium 
hydrate,  and  reacts  alkaline  to  turmeric  paper  and  to  reddened 
litmus. 

355.  Sodium    is    a    powerful   reducing    agent,    and   is 

largely  used  in  the  preparation  of  aluminium  and  mag- 
nesium. Its  amalgam  has  recently  been  employed  in 
the  reduction  of  silver  ores. 

Exp.  183. — Shake  together  in  a  test  tube  a  piece  of  sodium 
with  an  equal  bulk  of  mercury.  The  two  metals  will  combine 
with  a  sharp  flame,  and,  on  cooling,  form  a  solid  mass  (sodium 
amalgam).  This  may  be  employed  in  reducing  silver  chloride,  or 
reserved  for  experiments.  (See  Exp.  189). 


196  CHEMISTRY. 

356.  The   salts   of  sodium  arc,  perhaps,  the  most  im- 
portant  known    to    chemists.     Almost  every  acid  forms 
a  sodium  salt,  easily  soluble  in  Avater,  and  crystallizing 
from  concentrated  solutions  in  well-defined  forms.    Some 
of  these  have  received   a  wide    application    in    the   arts, 
and  therefore  require  a  more   extended    notice    than  we 
shall  be  able  to  give  to  those  of  the  metals  following. 

357.  Sodium  chloride,  NaCl,  is   our   common  salt  used 
in  cooking.     It  is  found  in  Europe  in  enormous  quanti- 
ties as  rock  salt.     In  the  United  States   it   is   generally 
obtained    by    evaporating    the    waters    of   salt    springs. 
Millions    of  tons    are    manufactured   annually   from    the 
salt   springs    of  New   York,   Michigan,   Ohio,   and  West 
\rirginia. 

Sodium  chloride  is  about  equally  soluble  in  cold  and 
hot  water.  A  saturated  brine  contains  about  26  per 
cent  of  salt.  From  such  saturated  solutions  the  salt 
crystallizes  out  in  beautiful  cubes,  which  sometimes  are 
so  attached  by  their  edges  as  to  form  hopper-shaped 
masses.  This  peculiarity  is  common  to  all  of  the  halo- 
gen compounds  of  the  alkalies. 

The  uses  of  salt  as  a  condiment  and  in  preserving 
meats  are  well  known.  It  also  finds  some  employment 
as  a  cheap  glazing  for  pottery,  and  is  the  source  from 
which  most  of  the  other  salts  of  sodium  are  obtained. 

358.  Sodium  sulphate,  Glauber's  salt,  Na2SO4-j- 10H2O, 
occurs  frequently  in  mineral  springs,  and  is  used  in  med- 
icine.     It    is    manufactured    in    enormous   quantities   by 
heating   sodium    chloride    with    sulphuric    acid.     In    this 
process    immense    quantities    of   hydrochloric    acid    are 
evolved,  which  are  absorbed  by  passing  the  gas  through 
towers  filled  with   coke  over  which   a   stream   of  water 
is  constantly  trickling.     The  operation   has  two  stages: 
(1)    The   acid   first   forms    an    acid   sodic  sulphate,  at  a 
comparatively  low  temperature;  thus,  NaCl  -j-  H2SO4  = 


SODIUM  COMPOUNDS.  197 

HaHSO4  -|-  HC1.  (2)  The  temperature  is  then  raised, 
when  the  acid  sodic  sulphate  acts  upon  the  remaining 
portion  of  the  salt  to  form  the  normal  sulphate,  NaCl  -|- 
JSTaHSO4  =  Na2SO4  +  IIC1.  The  product  thus  formed 
is  called  salt-cake.  If  dissolved  in  water  and  crystallized 
out  at  ordinary  temperatures,  it  retains  ten  molecules 
of  water  and  forms  monoclinic  prisms  which  effloresce 
in  dry  air. 

Exp.  184.— When  a  solution  of  this  salt,  saturated  at  33°  C., 
is  left  undisturbed  to  cool,  it  forms  a  so-called  supersaturated  solu- 
tion which  may  be  kept  for  days  without  crystallizing.  If,  after 
cooling,  a  crystal  of  the  salt  be  dropped  into  the  solution,  the 
whole  solidifies  to  a  mass  of  the  ordinary  crystals,  with  a  marked 
increase  of  temperature. 

359.  Sodium  carbonate,  Na2CO3,  is  made  by  roasting 
salt-cake   with   about   an    equal   weight   of  chalk  and  a 
little  more  than  half  its  weight  of  coal. 

The  chemical  change  consists  mainly,  (1)  in  the  action  of  the 
carbon  upon  the  sodium  sulphate,  whereby  sodium  sulphide  is 
formed:  Na2SO4  +  4C  =  Na2S  +  4  CO.  (2)  In  the  action  of  the 
carbon  upon  the  chalk,  whereby  the  calcium  carbonate  becomes 
calcium  oxide:  CaCO3  -f  C  =  CaO-f  2  CO.  (3)  "When  this  resulting 
mass  of  sodium  sulphide,  calcium  oxide,  and  unaltered  calcium  car- 
bonate is  treated  with  water,  there  forms  an  insoluble  oxy-sulphide 
of  lime,  and  sodium  carbonate  is  dissolved  out:  2Na2S  -f-  CaO  -)- 
2CaCO3  =2Na2CO3  -f  CaO,  2CaS.  (4)  The  solution  thus  obtained 
is  allowed  to  stand,  and  forms  crystals  of  the  formula  Na2CO3  -f- 
10 II 2  O.  These  crystals  easily  effloresce,  losing  their  water  of  crys- 
tallization and  becoming  anhydrous  Na2CO3. 

360.  The    "bicarbonate"    of   soda,    Na2O,  H20, 2CO2 
or  NaHCO3,  or  acid  sodium  carbonate,  is  easily  formed 
by  passing  into  a  solution  of  sodium  carbonate  a  stream 
of  carbonic  anhydride. 

Sodium  carbonate  is  largely  used  in  the  manufacture 
of  glass  and  of  soap,  and  is  the  usual  sal-soda  of  com- 
merce. Sodium  bicarbonate  is  used  in  medicine,  and  is 
one  of  the  constituents  of  most  baking  powders. 


198  CHEMISTRY. 

361.  Sodium   hydrate,    NaHO,    is   formed   by   heating 
sodium  carbonate  with  an  excess  of  slaked  quicklime. 

Na2CO3  +  Ca(HO)2  =  2NaHO  +  CaCO3. 

A  considerable  quantity  is  always  formed  in  the  process 
given  in  §  359,  because  of  the  excess  of  the  chalk  and 
coal  used.  When  its  solution  is  evaporated  to  dry  ness, 
it  forms  a  white,  solid,  fusible  mass,  soluble  in  water, 
with  considerable  evolution  of  heat.  It  is  a  very  strong 
base,  acting  very  caustic  upon  the  skin,  and  readily 
combining  with  oils  to  form  hard  soaps. 

362.  Sodium  nitrate,  NaNO3,  is  found  in  large  quan- 
tities in  Peru.    It  is  used  in  the  manufacture  of  blasting 
powder;    but   as    it   readily  deliquesces   in    moist   air,   it 
can   not   be   employed    for  the  manufacture  of  ordinary 
gunpowder.     It    finds    an    extensive    use    in    the    manu- 
facture of  ordinary  saltpeter,  nitric  acid,  and  fertilizers. 

363.  Di-sodium  phosphate,  Na2HPO4 -f  12II2O,  is  ob- 
tained by  adding  sodium  carbonate   to   phosphoric   acid 
or  to  its   lime   salt.     It  crystallizes   in   rhombic  prisms, 
which  effloresce  in  dry  air.     The   salt  dissolves  in    four 
parts  of  cold  water,  and   yields   a   solution   feebly  alka- 
line.    There  are  several  other  sodium  phosphates. 

364.  The    sodium    silicates    are    also    very   numerous, 
and,  at   the   same   time,  a  very  interesting  set   of  com- 
pounds.     When  caustic  soda  and  quartz  sand  are  fused 
together,  a  silicate    of  soda  is  formed.     The  formula  of 
the  resulting  compound  will  vary  with  the  proportions 
used,  as  silicic  acid  possesses  in  a  wonderful  degree  the 
property    of  forming    the    so-called    "  condensed "    salts. 
The  "  water  glass "    of  commerce    has  very    nearly   the 
formula  2Na2O,  5SiO2.     It   is   soluble  in   water,  and   is 
used    for    the    preparation    of   artificial    stone,    for    the 
manufacture   of  fire-proof  paints,   and    is    also    used    in 
some  kinds  of  soap. 


POTASSIUM.  199 

POTASSIUM. 

365.  Potassium  resembles  sodium  in  most  of  its  prop- 
erties,   and   is    frequently    found    associated    with    it    in 
nature.     It  exists  in  sea  water;  in  many  mineral  springs 
as  KC1.     Large   deposits   of  the  solid  chloride  have  re- 
cently been  discovered  at  Stassfurth.     It   is  also  a  con- 
stituent   of  the    common    feldspars    and    micas.     These 
minerals,  decomposing   through    atmospheric   influences, 
become  important  agents  in  soils,  and  yield  their  potash 
to  growing  plants.     From  these  it   is   again   transferred 
to   animals,   and    becomes    an    important   constituent  of 
milk,  blood,  and  flesh. 

The  principal  source  from  which  the  potassium  com- 
pounds are  obtained  is  the  ashes  of  plants.  When  a 
plant  is  burned,  the  organic  salts  of  potash  are  decom- 
posed and  the  carbonate  is  formed.  This  is  exhausted 
by  water,  and  forms  potash  lye. 

366.  The   manufacture    of  the   metal   is   effected   by 
heating  its  acid  tart-rate  in  closed  iron  retorts. 

(1)  At  a  low  heat,  the  tartrate  is  converted  into  an  exceedingly 
intimate  mixture  of  potassium  carbonate  and  charcoal.  (2)  This 
mixture  is  then  raised  to  a  white  heat;  the  metal  is  reduced  and 
distills  over:  K2CO3  -f  2C  =  2K  -f  3C"O.  (3)  The  product  is  re- 
ceived under  petroleum.  It  is  contaminated  with  a  black,  explo- 
sive compound  of  potassium  and  carbonic  oxide,  and  requires  to  be 
again  distilled  in  order  to  obtain  the  metal  in  a  pure  state. 

367.  Potassium  is  a  soft  metal,  having  a  bluish  tinge 
and  a  brilliant  luster.     At  0°  C.,  it  is   brittle;    at  ordi- 
nary temperatures    it   may  be   moulded    like   wax,  and 
two  fresh  surfaces  easily  welded  together.     It   melts   at 
62.5°  C.,  and  at  a  red  heat  volatilizes  with   a   beautiful 
green  vapor. 

It  is  one  of  the  lightest  of  metals :    sp.  gr.  0.86. 
It  is  strongly  electro-positive,  and  exhibits  a  remark- 
able affinity  for  oxygen.     When  exposed  to  dry  air,  its 


200  CHEMISTRY. 

surface  becomes  almost  immediately  covered  with  the 
protoxide  K2O.  It  decomposes  water  at  all  tempera- 
tures, and  with  sufficient  energy  to 
ignite  both  itself  and  the  hydrogen 
set  free.  The  flame  produced  is  a 
rich  violet,  and  is  characteristic. 

Owing  to  the  expense   of  manu- 
facturing potassium,  it   is   not   em- 
ployed in  the  arts,  being  replaced 
Flo.  ss.  by  its  congener  sodium. 

Exp.  185.  —  Make  a  small  cavity  in  a  lump  of  ice,  and  drop 
in  this  a  small  pellet  of  potassium.  It  will  take  fire  and  burn. 
Test  the  liquid  remaining  after  the  potassium  has  disappeared.  It 
contains  potassium  hydrate  and  reacts  alkaline. 


Exp.  186.  —  The  strong  affinities  of  potassium  may  be  further 
shown  by  (1)  placing  a  dried  pellet  in  a  deflagrating  spoon,  (2) 
melting  the  metal,  and  then  (3)  plunging  it  into  various  gases;  as, 
CO2,  Cl,  H2S.  It  decomposes  carbonic  anhydride,  setting  free  its 
carbon,  and  combines  with  chlorine  with  evolution  of  light. 

368.  Compounds    of   potassium.     When    the    ashes    of 
plants   are    lixiviated  with  water,  a  dark-colored    lye   is 
obtained  which  contains  all  the  soluble  salts  of  the  ash. 
This  lye,  boiled  down  to  dryness,  constitutes  the  crude 
"potash"  of  commerce.     It  consists  mainly  of  potassium 
carbonate;    it   also    generally    contains    some    potassium 
sulphate  and  some  sodium  salts.*     If  the  dark  color  of 
crude   potash    is  destroyed  by  roasting,  it  forms  "  pearl 
ash."     Pure    potassium    carbonate    is    best    obtained    by 
igniting  the  acid  tartrate  or  oxalate. 

369.  Potassium  carbonate,    K2CO3,   is   a   white,   deli- 
quescent salt,  very  readily  soluble   in   water.     It   has   a 
strong  alkaline  taste  and  reaction. 

*  In  some  American  potashes  there  exists  a  very  considerable  amount  of 
sodium  carbonate. 


POTASSIUM  COMPOUNDS.  201 

It  was  formerly  of  greater  importance  in  the  arts 
than  now;  but  is  still  very  largely  used  in  the  prepara- 
tion of  soft  soap,  of  some  kinds  of  glass,  and  in  the 
preparation  of  other  salts  of  potassium. 

370.  The  acid  potassium  carbonate,  KHCO3,  is  formed 
by  passing  carbonic   anhydride   through    a   solution   of 
the  preceding  in  four  parts  of  water.     Beautiful  mono- 
clinic  prisms  soon  separate  out.     It  was  formerly  much 
used,  under  the  name   of  saleratus,  in  baking  powders 
and  in  effervescing  drinks. 

When  the  acid  carbonate  is  heated,  it  loses  water  and 
half  of  its  carbonic  acid,  and  returns  to  the  state  of 
a  normal  carbonate.  No  amount  of  heat  will  expel 
the  carbonic  acid  remaining.  If,  however,  its  not  too 
concentrated  solution  is  treated  with  quicklime,  it  is 
decomposed  and  yields 

K2C03  +  Ca(HO)2  =  CaC03  +  2KHO. 

371.  Potassium    hydrate,    KIIO.     The    solution    thus 
formed  is  poured  off  and  evaporated  to  dryness  in  iron 
or  silver  vessels.     The   solid  hydrate  is  a  hard,  brittle, 
white,    deliquescent   mass,    fusible    below    red    heat.     It 
readily  absorbs   carbonic  anhydride    from    the    air;    but 
as  it  is  soluble  in   alcohol,  while    the   carbonate   is   not, 
an   alcoholic   solution   of  a   partially   altered   mass  will 
contain  only  the  hydrate. 

It  is  one  of  the  strongest  bases  known,  completely 
neutralizing  the  strongest  acids,  and  displacing  most 
other  bases  from  their  salts.  Its  taste  is  nauseous,  and 
its  solution,  when  concentrated,  is  highly  corrosive  to 
organic  tissues.  It  is  employed  in  medicine  as  a  caustic, 
whence  it  is  called  caustic  potash.  It  combines  with 
fats  to  form  soft  soaps. 

Exp.  187. — Add  a  solution  of  potassium  hydrate  to  any  salt 
of  iron  or  copper.  The  iron  or  copper  oxide  will  precipitate,  and 
the  potash  remain  in  solution,  combined  with  the  acid  of  the  salt. 


202  CHEMISTRY. 

372.  Potassium   chloride   and   potassium   chlorate   are 
formed  when  a  solution  of  potassium  hydrate  is  treated 
with  chlorine.     The  reaction  has  already  been  described 
(Art.    136).      The    Stassfurth    carnallite  (MgCl2,  KC1  -f 
6H2O)  promises  to  be  an  abundant  source  for  the  man- 
ufacture of  potassium  carbonate.     The  process  is  similar 
to  that  described    for   the   preparation    of  sodium    car- 
bonate. 

Similarly,  potassium  bromide  and  potassium  iodide 
are  formed  when  bromine  and  iodine  are  added  to  so- 
lutions of  potassium  hydrate  until  the  solution  becomes 
very  slightly  colored  :  GBr  +  6KHO  =  5KBr  +  KBrO8 
-j-3H2O.  Small  quantities  of  bromates  or  iodates  are 
formed  at  the  same  time.  These  may  be  separated  out 
by  crystallization,  or  decomposed  by  heating  into  oxygen 
and  the  halogen  salts. 

All  these  salts  (KC1,  KBr,  KI)  crystallize  in  cubes 
like  common  salt,  and  have  a  pleasant  saline  taste. 
The  two  latter  are  largely  employed  in  medicine  and 
in  photography. 

373.  There   are   five   potassium    sulphides.     We    shall 
describe    two    only.      If   sulphuretted    hydrogen    gas    is 
passed  into  potash  lye  to  full  saturation,  the  sulphydrate 
is  formed  :  KHO  +  H2S  =  KHS  +  H2O.    If  this  solution 
is  mixed  with  an  equal  quantity  of  the  potash  lye,  the 
monosulphide    is   formed:    KHS  + KHO  =  K2S  +  H2O. 
Both    of  these    salts,    when    treated    with    acids,    evolve 
sulphuretted  hydrogen,  and  are  used  to  form  sulphides 
of  many    of  the    metals    in    the    wet    way.     They    are 
strong  sulphur  bases,  and  easily  combine  with   the   sul- 
phides  of  arsenic,    antimony,    and   tin    to   form   soluble 
sulphur  salts. 

374.  Potassium   nitrate,  KNO3,  saltpeter,  occurs  nat- 
urally  in   the    soils   of  many  hot   countries,  and   as  an 
efflorescence  in  some  caverns.     It   is  formed   artificially 


GUNPOWDER.  203 

by  the  oxidation  of  nitrogenous  organic  bodies  in  the 
presence  of  strong  bases  like  lime.  Large  heaps  of  or- 
ganic matters,  mixed  with  old  mortar  and  lime,  are 
freely  exposed  to  the  air,  but  protected  from  rain  by  a 
roof.  These  heaps  are  moistened  from  time  to  time  with 
stable  drainings,  and  finally  lixiviated.  The  resulting 
calcium  nitrate,  when  treated  with  potassium  carbonate, 
yields  potassium  nitrate.  It  is  now  abundantly  pre- 
pared by  boiling  together  solutions  of  Chili  saltpeter 
and  potassium  chloride:  NaNO3+  KCl  =  KNO3-f-NaCl. 
The  sodium  chloride  first  crystallizes  out,  and  then  the 
saltpeter,  in  long  six-sided  prisms. 

The  principal  use  of  saltpeter  is  in  the  manufacture 
of  fireworks  and  gunpowder. 

Its  taste  is  saline  and  cooling.  When  heated,  it  melts 
at  340°  C.,  and  then  decomposes  into  oxygen  and  po- 
tassium nitrite.  From  the  ease  with  which  it  gives  up 
its  oxygen,  it  is  a  powerful  oxidizing  agent. 

Exp.  188. — Ignite  a  piece  of  charcoal  and  throw  upon  it  a 
little  saltpeter:  it  will  deflagrate  brilliantly. 

375.  Gunpowder  is  an  intimate  mixture  of  about  75 
parts  of  saltpeter,  13  parts  of  sulphur,  and  12  parts 
of  charcoal.  This  amounts  very  nearly  to  2KNO3-(- 
S-J-3C.  It  must,  however,  be  remembered  that  it  is 
not  a  compound,  but  a  mixture.  The  materials  are 
(1)  pulverized,  thrown  together,  moistened,  and  thor- 
oughly mixed  by  grinding  under  an  edge  mill.  (2)'  It 
is  then  subjected  to  great  pressure,  whereby  it  forms 
a  compact  mass.  (3)  This  is  broken  in  pieces  of  differ- 
ent sizes,  which  are  sorted  by  sieves.  (4)  The  powder 
is  then  dried  by  steam  heat,  and  is  frequently  glazed 
with  plumbago. 

When  gunpowder  is  fired,  its  explosive  force  is  due 
to  gaseous  products  such  as  CO2,  CO,  N,  and  O;  but 
besides  these  there  are  many  solid  products,  as  K2SO4, 
KaC08,  K3S,  etc. 


204  CHEMISTRY. 

Saltpeter  has  also  some   power   as   an   antiseptic,  and 


IS 


used  m  the  manufacture  of  nitric  acid. 


376,  Potassium   sulphate,  K2SO4,  is   a  by-product  in 
the  manufacture  of  nitric  acid.    When  an  excess  of  sul- 
phuric acid  is  used,  the  acid  potassium  sulphate  KHSO4 
forms.     The   latter,   heated   to   about   200°  C.,  gives   off 
water  and  forms  the  so-called  anhydrosulphate  K2S2O7 
or  SO3,K2,SO4.     At  a  still  greater  heat,  sulphuric   an- 
hydride is  evolved,  leaving  the  normal  sulphate  K2SO4. 

377,  Caesium  and  rubidium  are  very  widely  distributed 
in    mineral    waters   and  'the  ashes  of  many  plants,  but, 
nevertheless,    in    exceedingly    small    quantities.      More 
strongly  electro-positive   than    potassium,  they  resemble 
it  in  most  particulars,  but  are  distinguished  from  it  by 
the   greater   insolubility   of  their   salts,    and    the    colors 
which  their  salts  yield  in  the  spectrum.    (See  Art.  417). 

AMMONIUM. 

378,  When  a  solution  of  ammonia  in  water  is  neutral- 
ized by  an  acid,  a  salt  is  formed  which  is  very  similar 
to  the  corresponding  salt  of  potassium.     It  is  convenient 
to  consider  that  these  salts  contain  a  monatomic  radical 
ammonium,  NH4,  which  acts  like  an  atom  of  potassium, 
although    this    radical    has    never    been    isolated.      (See 
Art.  204). 

Exp.  189. — Add  to  a  strong  solution  of  ammonium  chloride  a 
pellet  of  sodium  amalgam.  (Exp.  183).  A  bulky  mass  of  the  con- 
sistence of  butter  forms,  which  was  once  thought  to  be  ammonium 
amalgam,  NH4Hgx.  However,  it  differs  in  many  respects  from 
sodium  amalgam,  and  soon  decomposes  into  mercury,  free  ammonia, 
and  hydrogen. 

379,  The    solution   of  ammonia   in  water  may  be  re- 
garded  as  NH4HO,   ammonium    hydrate,   or   aqua   am- 
monia.    It  corresponds  in  most  of  its  chemical  reactions 


AMMONIUM  COMPOUNDS.  205 

to  potassium  hydrate,  but  has  never  been  obtained  in 
the  solid  state.  It  smells  strongly  of  ammonia,  and 
readily  gives  off  this  gas  upon  boiling. 

380.  When  nitrogenous   bodies  decay,  or  when  horns, 
bones,  etc.,  are   subjected    to   destructive  distillation,  an 
impure    ammonium    carbonate    is    formed.      The    same 
product  is  found  in  the  ammoniacal  liquors  obtained  in 
the   manufacture   of  illuminating  gas  from  coal.     These 
liquors   are    now    the    chief  source   of  ammonium   salts. 
When    treated   with    quicklime,  they  yield   gaseous  am- 
monia;   with  sulphuric  acid,  ammonium  sulphate;    with 
hydrochloric  acid,  ammonium  chloride. 

381.  The   ammonium  chloride,  NH4C1,  thus  formed  is 
purified  by  first  evaporating  the  liquid  to  dry  ness,  and 
then  heating  the  dried  product.     The  ammonium  chlo- 
ride sublimes  without  previous  melting,  and  collects  in 
tough,  fibrous   masses   in    the   receiver.     It   dissolves   in 
its   own    weight   of  water  at   100°  C.,   and,  on   cooling, 
crystallizes  out  in  white,  feathery  aggregations  of  cubes 
or  octahedra. 

It  is  an  interesting  fact  that  the  vapor  of  ammonium 
chloride  has  but  half  the  density  due  to  theory  (1.86). 
To  account  for  this,  it  is  supposed  that  the  vapor  (two 
molecules)  is  decomposed  into  two  volumes  of  NH3  and 
two  of  HC1,  no  longer  combined,  and  therefore  not  con- 
densed. This  phenomenon  is  called  dissociation.  On 
cooling,  the  two  gases  again  combine. 

Ammonium  chloride  is  extensively  used  in  medicine. 
It  dissolves  many  oxides,  as  zinc,  and  hence  is  used  in 
soldering.  It  is  also  the  principal  source  from  which 
most  of  the  other  salts  of  ammonia  are  formed. 

382.  Ammonium  carbonate  is  made  by  heating  a  mix- 
ture of  ammonium  chloride  and  calcium  carbonate.    The 
carbonate   thus   formed   is   a  white,  easily  soluble  mass, 


206  CHEMISTRY. 

strongly  smelling  of  ammonia,  having  the  probable  for- 
mula of  2NH4O,  3CO2  +  3H2O.  It  is  the  sal-volatile 
of  the  apothecary. 

There  are  two  other  carbonates  of  ammonia.  The  acid  carbonate, 
NH4,  H,  CO3,  forms  when  the  preceding  sesquicarbonate  is  exposed 
to  the  air  as  a  white,  almost  odorless  powder,  somewhat  difficultly 
soluble  in  water.  The  normal  carbonate,  (NH4)2CO3,  has  never 
been  obtained  except  in  solution. 

383.  Ammonium   sulphate,    (NH4)2SO4,   is   important 
only  because  it  is  sometimes   used    in    the    manufacture 
of  other   ammonium  compounds,  especially  of  ammonia 
alum. 

384.  Ammonium  nitrate,  NH4NO3,   is   a  deliquescent 
salt,  very  easily  soluble    in  water.     When    the   dry  salt 
is  heated  gradually  to  about  240°  C.,  it  decomposes  into 
nitrous  oxide  and  water:  NII4NO8  =  ^O  -f  2II2O. 

385.  Microcosmic    salt,    Na,  NH4,  H,  PO4  +  4H2O,   is 

of  great  importance  in  blowpipe  operations.  When 
heated,  it  first  loses  its  water,  then  its  ammonia,  and 
becomes  a  glassy,  transparent  mass  of  sodium  meta- 
phosphate,  which  has  the  property  of  dissolving  many 
metallic  oxides  with  characteristic  colors. 

386.  Ammonium   sulphide,    (NH4)2S,  is  prepared   by 
saturating  aqua  ammonia   with    sulphuretted    hydrogen, 
and  then  adding  an  equal  quantity  of  aqua  ammonia. 

(1)  (NH4)HO-{-  H2S  =  NH4HS-fH2O. 

(2)  NH4HS  +  NH4HO  =  (NH4)2S  + H20. 

When  first  prepared  it  is  very  nearly  colorless,  but 
gradually  becomes  yellow,  or  even  red,  by  reason  of  the 
formation  of  higher  sulphides.  By  long  standing  it  is 
fully  decomposed,  with  separation  of  white  sulphur.  It 
is  a  very  important  agent  in  analytical  chemistry. 

Exp.  190.— Add  (NH4)2S  to  a  solution  of  a  zinc  salt.  White 
ZnS  separates  out. 


LITHIUM.  207 

Exp.  191.— Add  (NH4)2S  cautiously  to  a  solution  of  tartar 
emetic.  At  first,  an  orange  sulphide  of  antimony  precipitates;  but, 
on  adding  more  (NH4)2S,  it  redissolves  to  form  the  sulphantimonite 
(NH4)2S,Sb2S3. 

387.  Ammonium    bromide,    NH4Br,    and    ammonium 
iodide,   NII4I,   arc    colorless,   crystallizable    salts,   which 
are    extensively    used    in    photography    and    have    some 
employment  in  medicine. 

LITHIUM. 

388.  Lithium  is  the  lightest  of  the  metals,  floating  even 
upon  naphtha.     It  occurs  in  many  minerals  and  mineral 
springs;  notably  in  a  spring  in  Cornwall,  England,  which 
yields  daily  800  pounds  of  lithium  chloride. 

In  its  general  properties  it  resembles  sodium,  but  the 
sparing  solubility  of  its  carbonate  and  phosphate  ally  it 
to  magnesium.  It  may,  therefore,  be  regarded  as  a  con- 
necting link  between  the  alkalies  and  the  alkaline  earths. 

Its  citrate  and  carbonate  are  used  in  the  treatment 
of  rheumatism. 

Tests  for  the  Alkalies. 

(1)  All  alkaline  salts,  when  boiled  with  milk  of  lime,  yield  solu- 
tions   of  alkaline   hydrates.     These   solutions   turn   turmeric   paper 
brown,  and  restore  the  color  of  reddened  litmus.     Ammonia   alone 
yields  a  volatile  product,  which  may  be  recognized  by  its  peculiar 
odor,  and  by  its  yielding  white   fumes   in    the   presence   of  strong 
hydrochloric  acid. 

(2)  In    solutions    not   too   concentrated,    lithium    alone   yields    a 
precipitate  with  sodium  di-phosphate  and  sodium  carbonate. 

(3)  In    moderately  strong   solutions,    an    excess    of  tartaric  acid 
yields,  with  salts   of  NH4,  K,  Cs,  and  Kb,  white   crystalline  pre- 
cipitates of  acid  tartrates,  somewhat  freely  soluble  in  boiling  water. 

(4)  In    solutions    acidified    with    HC1,    platinum    tetrachloride, 
PtCl4,  yields  yellow  crystalline  precipitates   of  the  formula  2RC1, 
PtCl4,  with  salts  of  NH4,  K,  Cs,  Kb. 

(5)  K,    Cs,   Rb,    Li,   and   Na,    when    heated  in    a   non-luminous 
flame,  tinge  the  flame  with  characteristic  colors,  which  have   fixed 
places  in  the  spectrum.     (See  Spectrum  Analysis), 


208  CHEMISTRY. 

SILVER. 

389.  This    beautiful    metal    not    unfrequently    occurs 
native.     Its    most    abundant    ore    is    the    sulphide;    but 
this    is    generally    associated    with    other    sulphides,    as 
those    of  arsenic,    antimony,    and    lead.     It   occurs    less 
frequently  in  combination  with  Cl,  Br,  and  I. 

390.  The   method   of  extracting   silver  from   its   ores 
depends  upon  the  character  of  the  minerals  with  which 
it   is   associated.     The  so-called  amalgamation  process  is, 
perhaps,  the  most  common.    The  sulphides  are  (1)  roasted 
with  common  salt,  whereby  all  the    silver   is   converted 
into    silver   chloride.     (2)    The    resulting   mass    is    then 
mixed  with  iron  scraps  and  water,  and   placed  in  huge 
wooden  casks  which  are  made  to  revolve  by  machinery. 
The  silver  is  reduced  to  the  metallic  state,  2AgCl-|-Fe 

=  FeCl2  -f  2  Ag.  (3)  Mercury  is  then  added  in  sufficient 
quantity  to  form  a  fluid  silver  amalgam,  which  is  then 
drawn  off  from  the  earthy  matters  remaining,  and  washed. 
(4)  The  excess  of  mercury  is  pressed  out,  and  the  re- 
maining amalgam  heated  in  iron  retorts.  The  mercury 
distills  over,  and  metallic  silver  (often  containing  gold) 
remains  behind. 

391.  The   silver   produced  in  Europe  is  obtained  prin- 
cipally from  galena,  PbS,  which  very  generally  contains 
silver.     By  Pattison's  process,  lead   ores   containing  not 
more   than    three    ounces   to    the   ton    can  be  profitably 
worked.     (1)  On  smelting  the  ores,  all  the  silver  is  ob- 
tained   as   an    alloy    with    the    lead.     (2)    This   alloy    is 
melted  in   large   iron   kettles  and  allowed  to  cool  grad- 
ually.    Crystals    of  lead    form,    which    are    removed   by 
iron  strainers.     (3)   This   process    is   repeated    with    the 
residue  until  a  rich  alloy  of  silver  is  obtained.     (4)  The 
final  process  is  by  cupellation,  which  consists  in  oxidizing 
the   lead   in   a    shallow  vessel  made  of  bone  ash,  by  a 


SILVER   COMPOUNDS.  209 

flame  which  is  made  to  play  over  its  surface.  The  lead 
oxide  (litharge)  is  partly  driven  away  and  partly  sinks 
into  the  cupel,  while  pure  silver  remains  behind. 

392,  Pure   silver   does  not   oxidize  in  the   air;    but, 
when   in   the   melted  state,  has  the  curious  property  of 
absorbing  22  volumes  of  oxygen.    When  the  metal  cools, 
the   oxygen   escapes   and   bursts   through   the   solidified 
crust,  giving  rise   to   the  phenomenon  called  the  "  spit- 
ting of  silver."     Pure  silver  is  quite  soft,   and  is   never 
used  in  the  arts.     Silver   plate   and   coins   contain   ten 
per  cent  of  copper. 

Pure  silver  may  be  prepared  from  coin  by  (1)  dissolving  in 
nitric  acid;  (2)  precipitating  the  silver,  as  AgCl,  by  hydrochloric 
acid;  and  (3)  reducing  the  thoroughly  washed  silver  chloride  by 
zinc.  Thus  prepared,  it  is  a  brown  powder  which  may  be  melted 
at  1000°  C.  into  a  solid  mass. 

Silver  is  the  whitest  of  the  metals,  very  malleable 
and  ductile,  and  the  best  conductor  of  heat  and  of 
electricity.  It  readily  blackens  in  air  containing  sul- 
phuretted hydrogen,  owing  to  the  formation  of  silver 
sulphide.  It  is  scarcely  acted  upon  by  hydrochloric 
acid;  but,  when  heated  with  strong  sulphuric  acid,  dis- 
solves, forming  a  silver  sulphate  sparingly  soluble  in 
water:  2Ag -f  2H2SO4  =2H2O  +  362  +  Ag2SO4.  Its 
best  solvent  is  nitric  acid,  with  which  it  forms 

4Ag  +  6HN03  =  3H20  +  N2O3  +  4AgNO3. 

393,  Silver  nitrate,  AgNO3.     This   salt  crystallizes  in 
anhydrous,  rhombic  plates.     These  melt  at  219°  C.,  and 
form,  on  cooling,  a  hard  mass  which  is  used  by  surgeons 
under  the  name  of  lunar  caustic.     When  moistened  and 
applied  to  the  flesh,  it  quickly  and  completely  destroys 
the  vitality  of  the  part.     When  pure,  it   is   not   altered 
by  sunlight ;  but,  when  in  contact  with  organic  matters, 
soon    blackens    and   is    reduced    to   the    metallic    state. 

Chem.— 14. 


210  CHEMISTRY. 

Hence,  it  stains  the  skin  black ;  and  hence,  also,  its 
use  as  an  ingredient  of  indelible  ink  and  of  many  hair 
dyes.  It  is  the  only  salt  of  silver  freely  soluble  in 
water,  and  is  used  to  prepare  most  of  the  other  silver 
salts.  Sodium  hydrate  added  to  its  solution  precipitates 

394.  Silver  oxide,  Ag2O,  a  brown,  amorphous  powder, 
which  is  a  strong  base,  but  is  decomposed  by  heat  into 
oxygen  and  metallic  silver. 

395.  Silver   chloride,  AgCl,  is  readily  formed  from   a 
solution    of  silver   nitrate,  by  adding   to  it  IIC1  or  any 
soluble    chloride.     It    forms    a   white,   curdy   precipitate, 
insoluble  in  nitric  acid,  but  soluble  in  ammonia  and  in 
sodium  hyposulphite.     On  exposure  to  sunlight,  it  rap- 
idly blackens,  losing  chlorine  and  forming,  as  is  probable, 
a  sub-chloride  of  silver,  Ag2Cl.    Whatever  be  the  change, 
the   blackened   chloride    is    no   longer  soluble  in  sodium 
hyposulphite.     The  art  of  producing  photographs  upon 
paper  is  largely  dependent  upon  this  molecular  change. 

396.  Silver  bromide,  AgBr,  is  prepared  by  adding  to 
the  solution  of  the  nitrate  any  soluble  bromide,  as  KBr. 
It   has   a   yellowish    tinge,   and    is    somewhat   sparingly 
soluble  in  ammonia,  and  less  sensitive  to  light  than  the 
chloride. 

397.  Silver  iodide,  Agl,  precipitates  as  a  yellow  powder 
almost  insoluble  in  ammonia,  when  a  soluble  iodide,  as 
KI,    is    added    to   a   solution   of  silver    nitrate.     On    ex- 
posure to  light,  it  is   scarcely  altered  in  color,  loses   no 
iodine,  but  suffers  an  unexplained  molecular  change. 

398.  Photography,    as   now   practiced,    consists   essen- 
tially of  two  processes :  (I)  the  preparation  of  a  negative 
picture   on  glass;    (II)  the  printing  of  positive  pictures 
from  this  upon  paper. 

I.    (1)  A  clean  plate  of  glass  is  thinly  coated  with  a 
solution   of  collodion    containing  various  bromides   and 


PHOTOGRAPHY.  211 

iodides,  as  Cdl,  NH4I,  NH4Br.  This  rapidly  dries,  and 
forms  a  thin  but  coherent  film  upon  the  glass.  (2)  The 
plate  is  then  dipped  in  a  solution  of  silver  nitrate, 
whereby  a  sensitive  film  of  silver  iodide  and  bromide 
is  formed.  (3)  It  is  then  exposed  in  a  camera  for  a  few 
seconds.  The  film  does  not  suffer  any  visible  alteration, 
but  some  molecular  change  takes  place,  in  consequence  of 
which  a  latent  image  is  formed.  (4)  This  latent  image 
is  developed  by  pouring  upon  the  film  a  solution  of  fer- 
rous sulphate.  The  ferrous  sulphate  reduces  the  silver, 
which  has  been  acted  upon  by  the  light,  and  forms  a 
negative  picture;  that  is,  one  in  which  the  lights  and 
shades  of  an  ordinary  drawing  are  reversed.  (5)  The 
plate  is  then  protected  from  the  further  action  of  light 
by  washing  in  a  solution  of  sodium  hyposulphite,  to 
remove  the  unchanged  silver  salts,  and  then  in  a  large 
quantity  of  water.  (G)  The  film  is  finally  coated  with 
a  thin  film  of  varnish  to  protect  it  from  injury. 

II.  To  obtain  a  positive  picture  upon  paper,  or  one 
in  which  the  lights  and  shadows  are  in  their  natural 
positions,  (1)  a  sheet  of  white  paper  is  coated  upon  one 
side  with  a  layer  of  albumin  containing  ammonium  or 
sodium  chloride.  (2)  This  paper  is  rendered  sensitive 
by  washing  with  a  solution  of  silver  nitrate,  which  is 
thereby  converted  to  silver  chloride.  (3)  The  paper 
thus  prepared  is  placed,  when  dry,  behind  a  negative 
picture  and  exposed  to  the  sunlight.  (4)  The  exposed 
portions  of  the  chloride  are  reduced  and  blacken,  form- 
ing a  positive  picture.  (5)  It  remains  now  only  to  dis- 
solve out  the  unaltered  chloride  by  sodium  hyposulphite 
and  water,  in  order  to  render  the  picture  permanent ;  but, 
(6)  as  the  silver  thus  reduced  has  an  unpleasant  red  color, 
the  picture  is  "  toned,"  to  give  it  a  more  agreeable  tint. 
This  is  effected  by  steeping  the  paper  in  a  solution  con- 
taining a  little  gold  chloride  until  the  desired  tint  is  ob- 
tained. (7)  Finally,  it  is  again  washed,  dried,  and  mounted. 


212  CHEMISTRY. 

399.  Positive  pictures  may  also  bo  obtained  upon  glass, 
by  a  short  exposure  in  the  camera,  and  not  too  strong 
development.  They  are  then  placed  upon  a  dark  back- 
ground. The  reduced  silver  conceals  the  black  ground 
and  reflects  the  lights,  while  the  transparent  portions 
allow  the  black  ground  to  show  through,  and  thus 
represent  the  shadows  of  the  picture. 

TESTS. — Most  silver  suits  are  insoluble  in  water,  and  hence  a 
solution  of  silver  nitrate  yields  precipitates  with  phosphates,  arsenites 
(yellow);  arseniates,  chromates  (red);  oxalates,  chlorides,  bromides, 
iodides  (white  or  yellowish);  and  sulphides  (black).  All  of  these 
except  the  last  two  (Agl  and  Ag2S)  are  soluble  in  ammonia. 

A  sufficient  test  for  silver  in  its  solutions  is  obtained  by  adding 
HC1  to  them.  The  white,  curdy  AgCl  is  characteristic. 

Insoluble  silver  compounds,  mixed  with  dry  sodium  carbonate 
and  heated  upon  charcoal,  yield  a  globule  of  metallic  silver,  which 
may  be  dissolved  in  nitric  acid  and  tested  in  the  wet  way  — by 
K2Cr207,  HC1,  and  NH4HS. 

Recapitulation, 

Review  §351. 

The    alkali    metals    closely   resemble   each    other   in   their   physical 

properties. 
As  a  general  rule,  their  specific  gravities,  electro-positive  characters, 

and   the   basicity  of  their   hydrates    increase  with  their  atomic 

weights:    their  melting  points  decrease. 

Their  salts  are  generally  soluble  in  water. 

In  most  chemical  reactions,  the  compounds  of  any  one  of  them 
(and  of  ammonium)  may  take  the  place  of  any  corresponding 
compound  of  any  other:  allowance  must,  however,  be  made 
for  difference  in  solubility. 

Silver  differs  essentially  from  the  alkalies  in  its  high  specific  gravity 
and  melting  point,  as  well  as  in  its  weak  affinity  for  oxygen, 
and  the  difficult  solubility  of  most  of  its  salts  in  water. 


CHAPTER   XII. 

THE    DYAD    METALS. 


1 

^ 

0 

1 

B 

o 

H 

0 

H 

t£ 

K 

ft 

8 

ELEMENT. 

j 

o 

O 
O 

2 

o 

N 

DISCOVERER. 

a 

a 

1 

go 
D 

0 

03 

"* 

K 

h 

Calcium 

Ca 

40 

1.58 

Davy,            1808. 

Strontium 

Sr 

87.5 

2.5 

Davy,           1808. 

Barium 

Ba 

137 

4. 

450° 

Davy,           1808. 

Lead 

Pb 

207 

11.4 

325° 

Magnesium 

Mg 

24 

1.74 

433° 

Bussy,           1829. 

Zinc 

•Zn 

65 

7.1 

412° 

1040° 

Cadmium 

Cd 

112 

8.7 

320° 

860° 

Stromeyer,   1818. 

Mercury 

Hg 

200 

13.6 

—  39°.4 

350° 

Copper 

Cu 

63.4 

8.9 

1200°. 

400.  Calcium,  strontium,  and  barium  constitute  the 
group  of  the  alkaline  earths,  and  are  characterized  by 
strongly  marked  gradational  properties. 

The  metals  have  been  obtained  only  in  small  quantities 
by  the  electrolysis  of  their  fused  chlorides,  as  moderately 
hard,  yellowish  solids,  fusible  below  red  heat.  The 
chlorides  have  the  general  formula  EC12,  and  hence  these 
elements  are  dyad.  CaCl2  and  SrCl2  are  deliquescent 
and  are  soluble  in  alcohol;  BaCl2  is  not  deliquescent, 
and  is  not  soluble  in  alcohol. 

(213) 


214  CHEMISTRY. 

Their  compounds  resemble  those  of  the  alkalies,  and 
frequently  replace  them  in  commercial  operations.  Ba- 
rium has  the  greatest  chemical  activity,  and  possesses 
alkaline  properties  in  a  more  marked  degree  than  the 
others.  Its  hydroxide  Ba(OH)2  can  not  be  decomposed 
by  heat  alone,  and  is  easily  soluble  in  water.  The  ni- 
trates and  carbonates  of  this  group  may  be  decomposed 
by  heat,  yielding  anhydrous  oxides  of  the  formula  EO, 
which  readily  slake,  and  unite  with  water  forming  hy- 
droxides, like  Ca(OH)2.  Their  solutions  show  a  de- 
cidedly alkaline  reaction.  These  hydroxides  saponify  the 
fats,  but  the  resulting  soaps  are  insoluble  in  water. 
These  elements  also  form  peroxides  RO2,  which,  when 
decomposed  by  dilute  hydrochloric  acid,  yield  peroxides 
of  hydrogen,  II2O2.  Their  carbonates,  phosphates,  and 
sulphates  are  nearly  insoluble  in  water.  Their  most 
abundant  sources  are  their  carbonates  and  sulphates, 
which  are  often  found  associated  together. 

401.  Lead  is  added  to  this  group  because  many  of  its 
salts  are  similar  to  those  of  barium.  Its  carbonate, 
phosphate,  and  sulphate  are  insoluble  in  water.  It  acts 
as  a  dyad  metal  in  most  of  its  compounds,  as  PbCl2, 
PbO ;  but  sometimes  acts  as  a  tetrad,  especially  in  some 
organic  compounds,  as  Pb,  (C2H5)4,  plumbic  ethide. 


CALCIUM. 

402.  The  compounds  of  calcium  are  very  widely  and 
abundantly  distributed.  They  occur  in  enormous  quan- 
tities as  carbonates,  in  marble,  chalk,  and  limestone; 
as  sulphates,  in  gypsum  and  alabaster;  as  silicates,  in 
many  minerals,  e.  g.  labradorite ;  and  less  frequently  as 
fluorides,  in  fluor  spar.  It  is  also  an  almost  invariable 
constituent  of  vegetables  and  animals,  being  especially 
concentrated  in  shells,  corals,  teeth,  and  bones. 


COMPOUNDS  OF  CALCIUM.  215 

403.  Calcium   carbonate,  CaCO3,  has  a  great  variety 
of  crystalline  forms  which  are  referable  to  two  systems : 
(1)  the  hexagonal,  represented  by  Iceland  spar ;  (2)  the 
trimetric,  represented   by  aragonite.     It  is  found  in  the 
ashes   of  plants,   in   egg-shells,  in  bones,  corals,  and  in 
the  shells  of  mollusks.     The   enormous  masses  of  lime- 
stone, which  serve  as  building  stones,  are  largely  made 
up  of  the  broken  and  pulverized  forms  of  the  two  latter. 
It  is  prepared  artificially  by  adding  ammonium  carbonate 
to  a  solution  of  calcium  chloride. 

Calcium  carbonate  is  almost  insoluble  in  water.  Waters 
containing  free  carbonic  anhydride  dissolve  it  more  freely, 
forming  the  so-called  calcareous  mineral  waters.  They 
contain,  probably,  acid  calcium  carbonate,  CaH2  (CO3)2. 
This  salt  has  not  been  obtained  in  the  solid  state,  be- 
cause, when  these  waters  are  evaporated,  they  lose  a 
molecule  of  carbonic  anhydride,  and  yield  a  precipitate 
of  calcium  carbonate.  Hence,  such  mineral  waters  de- 
posit naturally,  on  exposure  to  the  air,  their  calcium 
carbonate,  forming  tufa,  stalactites,  etc.,  or  yield  it  up 
upon  boiling,  forming  the  incrustations  of  boilers.  Such 
waters  are  said  to  have  a  "  temporary  hardness."  This 
hardness  is  removed  by  boiling,  or  by  the  addition  of 
calcium  hydrate  in  sufficient  quantity  to  form  the  insol- 
uble normal  carbonate. 

Exp.  192. — (1)  Pass  into  a  solution  of  calcium  hydrate,  diluted 
with  an  equal  amount  of  water,  a  stream  of  carbonic  anhydride: 
calcium  carbonate  precipitates.  (2)  Continue  the  operation,  and 
the  calcium  carbonate  again  dissolves.  Now  divide  the  product 
into  two  parts.  (3)  Boil  one,  and  observe  that  it  soon  becomes 
turbid.  (4)  To  the  other  portion  add,  gradually,  a  solution  of  cal- 
cium hydrate,  and  observe  the  same  turbidity,  being  in  both  cases 
due  to  precipitated  calcium  carbonate.  Upon  the  latter  reaction 
rests  Clark's  process  of  softening  calcareous  waters. 

404.  Calcium  oxide,  CaO,  or  quicklime,  is  formed  when 
calcium  carbonate  is  heated  to  redness  in  the  open  air. 


216  CHEMISTRY. 

It  is  a  white,  amorphous,  infusible  mass.  When  water 
is  poured  upon  quicklime,  the  two  combine  quickly 
with  great  evolution  of  heat,  and  the  quicklime  crum- 
bles to  a  white  powder,  which  is  calcium  hydrate: 
CaO  +  II2O  =  Ca(HO)2.  This  is  the  slaking  of  lime. 
When  exposed  to  the  air,  quicklime  gradually  absorbs 
moisture  and  forms  air-slaked  lime.  Calcium  hydrate 
dissolves  in  about  700  parts  of  cold  water  to  form  a 
feebly  alkaline  and  caustic  solution.  It  readily  absorbs 
carbonic  acid,  and  is  used  as  a  test  for  it. 

405.  Calcium  hydrate  suspended  in  water  forms  "  milk 
of  lime."  Its  caustic  property,  together  with  its  strong 
affinity  for  carbonic  anhydride,  renders  it  a  useful  agent 
(1)  in  tanning,  to  remove  hair  from  hides;  (2)  inform- 
ing, with  fats,  insoluble  soaps,  which  are  afterward  em- 
ployed in  preparing  stearine  candles;  (3)  in  the  prep- 
aration of  caustic  alkalies;  (4)  in  purifying  coal  gas. 
(5)  When  mixed  with  sand,  it  is  ordinary  mortar.  This, 
as  it  dries,  becomes  a  mixture  of  calcium  carbonate  and 
calcium  silicate,  capable  of  binding  stones  and  bricks 
firmly  together.  Hydraulic  cements,  which  have  the 
property  of  hardening  under  water,  contain  from  15  to 
30  per  cent  of  alumina  and  silica  (clay),  and  frequently 
some  magnesia.  (G)  It  is  also  largely  used  in  the  man- 
ufacture of  the  "chloride  of  lime,"  used  in  bleaching 
cotton  goods.  The  process  consists  simply  in  passing 
chlorine  gas  over  slaked  lime,  whereby  a  calcium  chlo- 
ride and  hypochlorite  are  simultaneously  formed, 

2Ca(HO)2  -fCl4=CaC]2  +  Ca(ClO)2  +  2II2O; 

always,  however,  mixed  with  an  excess  of  calcium 
hydrate.  This  mixture,  treated  with  water,  yields  an 
impure  solution  of  calcium  hypochlorite,  which,  when 
treated  with  dilute  acids,  yields  either  hypochlorous 
acid  or  free  chlorine,  and  is,  therefore,  a  powerful 
bleaching  and  disinfecting  agent. 


COMPOUNDS  OF  CALCIUM.  217 

When  this  solution  is  boiled,  the  chlorate  is  formed, 
3Ca(ClO)2^2CaCl2  +  Ca(ClO3)2,  whence  it  is  econom- 
ically used  in  the  preparation  of  potassium  chlorate: 

Ca(ClO3)2  +  2KC1  =  CaCl2  +  2KC1O8. 

406.  Calcium  chloride,  CaCl2,  which   is  a  by-product 
in   the   last   process,   is   more    advantageously   prepared 
for  laboratory  purposes  by  the   action   of  hydrochloric 
acid  upon  calcium  carbonate : 

CaC03  +  2HC1  =  Ct>2  +  H20  +  CaCl2. 

It  crystallizes  from  strong  solutions  in  transparent  prisms, 
CaCl2,6H2O.  These,  mixed  with  snow,  form  a  freezing 
mixture,  reducing  the  temperature  to  --48°  C.  (more 
than  sufficient  to  solidify  mercury).  When  heated  to 
200°  C.,  they  become  anhydrous;  and,  on  cooling,  form 
a  porous  mass  extremely  deliquescent,  and  therefore 
largely  employed  as  a  desiccating  agent  in  drying  gases. 

407.  Calcium    sulphate,    CaSO4,    is   soluble    in   about 
400  parts  of  water  at  ordinary  temperatures,  and  about 
460  parts  at  100°  C.     Hence,  it  is  not  entirely  expelled 
by  boiling,  and  is  one  of  the  causes  of  the  "  permanent 
hardness"   of  water.     It   is   somewhat   more   soluble  in 
salt  waters ;  but,  when  these  are  evaporated,  crystallizes 
out  much  sooner  than  the  common  salt.     In  nature  we 
find  it  frequently  associated  with   beds   of  rock-salt   as 
gypsum  and  alabaster,  CaSO4,  2H2O.     When  gypsum  is 
heated   it   loses   its  water  of  crystallization ;  and,  if  not 
heated    beyond    250°    C.,    retains    the    power    of   again 
uniting   with    the   water,   and    setting   to    a   hard   mass. 
This  calcined  gypsum  is  the  "plaster  of  Paris"  used  in 
stucco-work,  in  making  casts,  and  as  a  valuable  fertilizer. 

Exp.  193.— (1)  Sift  into  a  small  quantity  of  water  ground 
plaster  of  Paris  until  it  rises  to  the  surface.  On  stirring  this  it 
forms  a  pasty  mass.  (2)  If,  now,  this  is  poured  into  a  suitable 
mould,  it  "sets,"  or  hardens,  at  the  same  time  expanding  so  as 


218  CHEMISTRY. 

to  fill  every  cavity  of  the  mould.  (3)  In  a  short  time  it  will  be 
so  hardened  that  it  can  be  removed,  and  will  then  present  an  exact 
reverse  copy  or  cast  of  the  mould.  (4)  To  prevent  the  cast  clinging 
to  the  mould,  it  is  only  necessary  previously  to  smear  it  carefully 
with  oil. 

408.  Calcium   phosphate,   Ca3(PO4)2,    is   very  widely 
diffused  in  soils,  though  not  very  abundant.     It  is  taken 
up   by   plants,   especially  by  cereals,  like  wheat,  and  is 
the  chief  inorganic  constituent  of  the  bones  of  animals. 
(See  Arts.  227  and  228). 

COMPOUNDS  OF  STRONTIUM. 

409.  Strontium   occurs  somewhat  sparingly  in  nature 
as  a  carbonate,  SrCO3  (strontianite),  and  as  a  sulphate, 
SrSO4  (coelestine).     These  salts  are  used  only  as  sources 
of  the  soluble  salts. 

The  best  source  of  strontium  compounds  is  the  car- 
bonate, which  is  readily  soluble  in  nitric  and  hydro- 
chloric acids.  They  are  also  prepared  from  the  sulphate 
by  (1)  roasting  it  with  charcoal,  whereby  it  is  converted 
to  a  soluble  sulphide  (SrSO4  -f  4C  =  4dl)  -f  SrS),  and 
(2)  dissolving  the  crude  product  in  hydrochloric  or  nitric 
acid,  SrS  +  2HNO8  ==  H^S  +  Sr(NO8)2. 

410.  Strontium  nitrate,   Sr(NO3)2,   is  readily  soluble 
in  water,  but  is  insoluble  in  alcohol.     It  is  used  in  fire- 
works   for    the    preparation    of  crimson    flames.     "When 
strongly   ignited,    it  yields  strontium  oxide,  SrO,  a  body 
similar  to   quicklime ;    but,  on   slaking,   is   more   soluble 
in  water,  and  yields  a  more  caustic  solution.     Strontium 
chloride,    SrCl2,    is    freely    soluble    both    in    water    and 
alcohol. 

BARIUM  COMPOUNDS. 

411.  The   principal  native  compounds   of  barium  'are 
also  the  carbonate  (witherite)  and   the   sulphate  (heavy 


BARIUM  COMPOUNDS.  219 

spar).  The  sulphate  is  extensively  used  as  a  pigment, 
under  the  name  of  "  permanent  white,"  in  adulterating 
white  lead,  and  in  the  manufacture  of  paper,  to  give 
weight. 

Its    soluble    compounds    are    obtained    like    those    of 
strontium. 

412.  Barium  nitrate,  Ba(NO3)2,  is  insoluble  in  alcohol, 
but   soluble    in    12    parts   of  cold   water.     It  is   used   in 
fireworks   to    prepare    green    flames.     When    ignited,    it 
yields  barium  oxide,  BaO,  which  is  soluble   in   20   parts 
of  cold   water,  yielding   a    strongly    caustic   solution    of 
barium  hydrate,  Ba(HO)2.     It  rapidly  absorbs  carbonic 
anhydride  from  the  air,  and  is  used  for  the  volumetric 
determination  of  that  gas. 

413.  Barium    peroxide,   BaO2,  is  an  interesting   com- 
pound, prepared  by  heating  barium  oxide   in  a  current 
of  air  or  of  oxygen.     If,  now,  the  temperature  be  slightly 
raised,  and  steam  be  passed  over  the  peroxide,  oxygen 
will   be   given  off  and  barium  oxide  will  remain.     It  is 
proposed   to   prepare   oxygen  on  a  large  scale  by  using 
these  reactions  alternately.     (See  Art.  114). 

414.  Barium  chloride,  BaCl2,  crystallizes   in   rhombic, 
non-deliquescent  plates.     They  are  soluble  in  water,  but 
not  in    alcohol.     Its    principal    use    is   in   the   detection 
of  sulphuric  acid. 

415.  All   the   soluble   salts    of  barium    are    poisonous. 
Any  soluble  sulphate,  as  Epsom  salts,  may  be  given  as 
an  antidote. 

416.  Tests. — Most   of  the   tests   for  the  metals  depend 
upon    the    fact    that    certain    reagents,    when    added    to 
their   solutions,   form    new  compounds   of  sparing  solu- 
bility. 

These    new   compounds,    if  insoluble,    separate   out    at   once;    if 
difficultly  soluble,  at  once  in  strong  solutions,  but  only  after  a  time 


220  CHEMISTRY. 

in  dilute  solutions;  if  moderately  soluble,  only  in  somewhat  concen- 
trated solutions;  if  freely  soluble,  not  until  the  solutions  are  so 
concentrated  by  evaporation  that  the  point  of  crystallization  is 
reached. 

The  delicacy  of  such  reactions,  therefore,  depends  on  the  insolu- 
bility of  the  new  compound  formed. 

(1)  All   carbonates,    phosphates,   and    sulphates    of   the    calcium 
group    are   either   insoluble   or  difficultly  soluble   in   water.     They 
are   formed    as    white    precipitates    when    any    alkaline    carbonate, 
phosphate,  or  sulphate  is  added  to  solutions  of  their  salts. 

(2)  Calcium   sulphate   is   soluble   in   400  parts  of  water,  and  its 
solution    may  be   used   for   the    detection   of   Ba   and   Sr.     Barium 
sulphate  is  quite  insoluble,  and  strontium  sulphate  nearly  so. 

(3)  Ammonium  oxalate  also  forms  a  white  precipitate  with  these 
salts.     When    free   oxalic   or   acetic   acid    is   present,  only  calcium 
oxalate  precipitates.     This  is  a  very  characteristic  test  for  calcium. 

(4)  Potassium    chromate   produces   an    almost    insoluble   barium 
chromate,    a   moderately   soluble   strontium   chromate,  and  a  freely 
soluble  calcium  chromate.     Hence,  a  solution  of  strontium  chromate 
is  a  characteristic  test  for  barium. 

(5)  All  these  salts  tinge  a  colorless    flame  with    a   characteristic 
color:  calcium,  brick-red;    strontium,   crimson;    and  barium,  green. 
When   examined   by  the   spectroscope,  these  colors   yield   lines   of 
definite  refrangibility. 

SPECTRUM  ANALYSTS. 

417.  Most  compounds  of  the  alkalies  and  of  the  cal- 
cium group,  arc  readily  volatile.  When  heated  in  the 
almost  non-luminous  flame  of  a  Bunsen's  burner,  they 
yield  colored  flames  which  are  often  sufficiently  char- 
acteristic to  be  determined  by  the  eye.  If,  however, 
these  colored  flames  are  passed  through  a  prism,  each 
flame  is  found  to  yield  one  or  more  colored  lines  which 
have  a  fixed  place  in  the  spectrum,  and  are  therefore 
characteristic  for  each  element.  Upon  these  facts  the 
spectrum  analysis  is  based. 

The  spectroscope  (Fig.  89)  is  used  for  examining  colored  flames. 
The  substance  to  be  tested  is  volatilized  upon  a  platinum  wire  in 
a  Bunsen's  burner  at  E.  The  flame  is  passed  through  a  narrow 


SPECTRUM  ANALYSIS. 


221 


slit  in  the  tube,  A,  and  thrown  upon  the  prism,  P.  The  light  is 
refracted  by  this  prism  in  rays  of  definite  refrangibility,  which  fall 
upon  the  object-glass  of  the  telescope,  B,  and  pass  through  it  to 
the  eye.  In  this  way,  with  a  single  prism  and  at  moderate  tem- 
peratures, it  is  found  that  sodium  yields  but  one  yellow  line; 
lithium,  a  bright  red  line  and  a  fainter  orange;  potassium,  two 
lines — one  red  and  the  other  violet;  thallium,  one  green  line.  The 
spectra  of  the  calcium  group  are  more  complex.  Strontium  yields 
six  red  lines,  one  orange,  and  one  blue  line;  calcium,  several  lines, 
two  of  which,  a  green  and  an  orange,  are  especially  characteristic; 
and  barium,  a  large  number  of  green  lines. 


FIG.  89. 

In  order  to  fix  the  place  of  these  lines,  a  tube,  C,  is  added.  It 
contains  at  one  end  a  transparent  scale  of  equal  parts.  "When  this 
scale  is  illuminated  by  a  bright  light,  it  casts  a  bright  image  on 
the  prism,  which  is  reflected  by  the  prism  into  the  telescope,  B, 
so  that  the  observer  can  fix  the  exact  position  of  the  lines  produced 
by  the  flame  which  he  is  examining.  In  the  first  scale  constructed 
by  Bunsen,  the  sodium  line  coincided  with  the  line  50;  lithium, 


222  CHEMISTRY. 

with  31  and  45,  etc.  *  It  was  also  found  that  these  lines  were 
always  characteristic,  and  that,  in  a  mixture,  each  element  yielded 
its  characteristic  lines,  as  if  it  were  volatilized  alone.  No  chemical 
test  rivals  this  in  the  delicacy  of  the  reaction.  Bunsen  calculated 
that  he  had  found  ygooooooo  of  a  grain  of  sodium,  and  could  be 
certain  of  ZQ^-Q-Q  of  a  grain  of  caesium. 

The  method  here  described  is  the  only  one  used  in  the  chemical 
laboratory.  It  must,  however,  be  added  that,  at  higher  tempera- 
tures (as  that  of  the  electric  spark),  and  by  using  a  train  of  prisms, 
other  lines  are  found  and  other  metals  volatilized,  yielding  numerous 
and  characteristic  lines. 

To  the  invention  of  the  spectroscope  we  owe  the 
discovery  of  caesium,  rubidium,  thallium,  indium,  and 
gallium. 

LEAD. 

418.  Many  lead  compounds  occur  in  nature,  but  by 
far  the  most  abundant  is  the  sulphide,  or  galena,  PbS. 
The  reduction  of  the  sulphide  is  effected  in  reverbera- 
tory  furnaces,  in  which  the  dressed  galena  (1)  is  roasted 
at  a  gentle  heat  in  a  current  of  air.  The  lead  sulphide 
is  thereby  converted  partly  into  lead  oxide  and  partly 
into  lead  sulphate: 


(2)  The  furnace  is  then  closed  and  the  temperature 
raised,  whereby  the  undecomposed  sulphide  reacts  upon 
the  products  already  formed  to  produce  metallic  lead  : 

(1)       2PbO    -f  PbS  =     SO  2  +  3Pb. 


(2)       PbSO4  +  PbS  =  2       2  -f  2  Pb. 

419.  Lead,  when  freshly  cut,  is  a  bluish  gray  metal, 
at  first  lustrous,  but  soon  becoming  oxidized.  It  is  very 
malleable,  but  of  inferior  ductility  and  tenacity;  so  soft 
as  to  leave  a  streak  when  rubbed  upon  paper,  and  melts 
at  325°  C.  Its  molten  surface,  when  exposed  to  the  air, 

*  The  scale  is  arbitrary  and  differs  with  each  instrument, 


LEAD.  223 

rapidly  oxidizes  to  litharge,  PbO ;  and,  by  longer  heating, 
to  red  lead,  Pb3O4  or  2PbO,  PbO2. 

Exp.  194. — Heat  dry  tartrate  of  lead  in  a  hard  glass  tube  until 
the  tartaric  acid  has  been  decomposed;  then  cork  the  tube  tightly, 
and  allow  it  to  cool.  It  contains  a  mixture  of  carbon  and  finely 
divided  lead  (lead  pyrophorous}.  On  pouring  this  out,  it  will  take 
fire  and  burn  to  litharge. 

Hydrochloric  and  sulphuric  acids  exert  only  a  surface 
action  upon  lead.  Its  best  solvent  is  nitric  acid,  some- 
what diluted.  It  is  also  corroded  by  acetic  acid  vapors 
in  the  presence  of  air  and  moisture.  The  acetate  and 
nitrate  are  readily  soluble  in  water,  and  may  be  used 
in  forming  the  insoluble  compounds  of  lead. 

420.  Lead  nitrate,  Pb(NO3)2,  crystallizes  in  octahedra. 
It  is  decomposed  at  a  low  red  heat  into  oxygen,  nitric 
peroxide,  and  litharge.     Common  litharge  is  an  impure, 
yellow  protoxide,   obtained    in    large   quantities   by  the 
cupellation   of  silver.     Heated   for  some  time  below  its 
point  of  fusion  (about  400°  C.),  it  oxidizes  further  and 
forms  red  lead.     This  oxide,  which  is  sometimes  used  as 
a  paint,  is  decomposed  by  nitric  acid, 

Pb804  +  4HN03  =  2Pb(N03)2  +  2H20  +  PbO2, 

yielding  lead  nitrate,  water,  and  lead  dioxide  (PbO2), 
the  last,  a  brown  powder  which  is  capable  of  forming 
salts  with  both  acids  and  bases.  Like  many  other  per- 
oxides, when  treated  with  hydrochloric  acid,  it  evolves 
chlorine  and  forms  a  chloride. 

421.  Lead  chloride,   PbCl2,  is  soluble  in  33  parts  of 
water,  and  forms  as  a  white  crystalline  precipitate  when 
hydrochloric  acid  is  added  to  a  strong  solution   of  any 
lead  salt. 

422.  Lead  carbonate,    PbCO3,   is   formed   as   a  white 
precipitate  on  adding  ammonium  carbonate  to  a  solution 
of  any  lead  salt. 


224  CHEMISTRY. 

The  commercial  (l  white  lead "  is  prepared  on  a  large  scale  by 
(1)  exposing  plates  of  lead  in  earthen  jars  to  the  fumes  of  vinegar, 
whereby  it  is  converted  into  a  basic  acetate;  (2)  then  burying  them 
in  large  heaps  of  tan-bark.  This  slowly  decays,  evolving  carbonic 
anhydride,  which  converts  the  acetate  into  a  basic  carbonate,  and 
(3)  sets  free  the  acetic  acid  to  act  upon  fresh  portions  of  the  lead. 

White  lead  has  greater  opacity,  or  "body,"  than  the 
precipitated  carbonate,  and,  when  ground  with  linseed 
oil,  forms  the  basis  of  ordinary  white  paints. 

423.  Lead  sulphide,  PbS,  occurs  native  as  galena,  and 
may  be  formed  artificially  by  passing   sulphuretted   hy- 
drogen   through    any  solution    of  lead   salts.     This  is  a 
black,   amorphous   powder,   soluble   in    nitric   acid   with 
liberation  of  sulphur. 

424.  The  soluble  lead  salts  are  all  poisonous ;  and,  as 
lead    pipes   are  often  used  to  convey  water,  it  is  neces- 
sary to    consider   the    action    of  water   upon    lead.     (1) 
Pure  water  free  from  air  does   not   act    upon    lead.     (2) 
If  the   water   contains  air,  the  lead  oxidizes,  forming  a 
slightly  soluble  hydrate.     (3)  If,  in   addition,  the  water 
contains  chlorides,  nitrates,  nitrites,  or  decomposing  or- 
ganic   matters,    the    oxide    formed   is   dissolved,  and  the 
water    may   be    seriously    contaminated    with    poisonous 
lead  salts. 

On  the  other  hand,  (4)  if  the  water  contains  phos- 
phates, sulphates,  and  especially  carbonates,  the  hydrate 
will  be  changed  to  an  insoluble  salt,  which  protects  the 
lead  from  further  action.  Such  waters  are  generally 
innocuous ;  but  (5)  it  must  be  borne  in  mind  that  the 
lead  carbonate  is  slightly  soluble  in  water  containing 
free  carbonic  anhydride.  Hence,  (6)  when  drinking 
waters  are  conveyed  through  leaden  pipes,  it  is  safe  to 
use  them  only  when  enough  has  run  through  to  guar- 
anty that  they  are  uncontaminated  with  lead. 

The  antidotes   for   lead   poisoning   are  the  soluble  sulphates,  as 


THE  MAGNESIUM  GROUP.  225 

Epsom  salts.     Weak  sulphuric  acid  is  recommended   as   a  prophy- 
lactic for  workmen  engaged  in  the  manufacture  of  its  compounds. 

425.  The  alloys   of  lead   are    numerous.     Type   metal 
contains  about  20  per  cent  of  antimony,  and   is   distin- 
guished   not   only   for    its   great    hardness,   but   for   the 
sharp  casts  which   it   gives,  owing   to    its   expansion    at 
the  moment   of  solidification.     Soft   solder,  which  melts 
at  186°  C.,  is  an  alloy  of  nearly  equal  parts  of  lead  and 
tin.     Shot  is  lead   hardened  by  about   two  per  cent  of 
arsenic. 

426.  Tests  for  lead.     Lead  resembles  the  metals  of  the 
calcium  group  in  the  fact  that  alkaline  carbonates,  phos- 
phates, and  sulphates,  when   added   to   solutions   of  its 
salts,    produce    insoluble    precipitates.      It    differs    from 
them   in    the    stability   of  the    metal,    its   high    specific 
gravity,    by    the    ready   reducibility   of  its    compounds, 
and  by  the  following  reactions. 

All  lead  compounds,  when  mixed  with  dry  sodium  carbonate, 
are  readily  reduced  before  the  blowpipe,  and  yield  a  malleable  me- 
tallic bead.  This  bead,  dissolved  in  nitric  acid,  or  any  lead  salt  in 
solution,  yields — 

(1)  With  sulphuretted  hydrogen  or  ammonium  sulphide,  a  black 
lead  sulphide,  insoluble  in  dilute  acids; 

(2)  With  hydrochloric  acid,  a  white  precipitate  soluble  in  a  large 
excess  of  boiling  water; 

(3)  With  potassium  iodide  or  potassium  chromate  in  neutral  so- 
lutions, a  yellow  precipitate. 

THE  MAGNESIUM  GROUP. 

427.  Magnesium,  zinc,  and  cadmium  have  many  prop- 
erties in  common,  and  yet  present   marked    differences. 
They  are  malleable  and  somewhat  ductile  metals  which 
remain    unaltered    in    dry    air;    but,    on    being    heated, 
volatilize    at   high    temperatures ;    and,   in    the  presence 
of    oxygen,    burn,    forming    bulky    anhydrous    oxides. 

Chem.— 15, 


226  CHEMISTRY. 

These  oxides  are  nearly  insoluble  in  water,  but  readily 
combine  with  acids,  forming  salts  which,  in  most  cases, 
are  isomorphous.  Their  basic  power  diminishes  with  an 
increase  in  atomic  weights.  .Magnesium  is  the  most  elec- 
tro-positive of  this  group.  It  decomposes  boiling  water 
rapidly,  while  zinc  and  cadmium  act  slowly. 

On  the  other  hand,  magnesium  sulphide  is  decomposed 
by  water;  zinc  sulphide  is  soluble  in  dilute  acids  (ex- 
cepting acetic) ;  and  cadmium  sulphide  is  insoluble  in 
dilute  acids. 

It  needs  also  to  be  remarked  that  magnesium  is  re- 
lated to  lithium  through  the  insolubility  of  its  carbonate 
and  phosphate,  and  to  calcium  through  the  isomorphism 
of  their  carbonates.  All  the  metals  of  this  group  differ 
from  those  of  the  calcium  group  in  the  fact  that  their 
sulphates  are  soluble  in  water. 

MAGNESIUM. 

428.  Magnesium    occurs    in    nature    as    a    carbonate 
(magnesite).     Usually  this  carbonate    is  associated  with 
lime,    as    dolomite    (MgCO3  -f  CaCO3),    or    is    found    in 
enormous    masses    as    magnesian    limestone.     It    is    also 
found  as  a  silicate  in  talc,  serpentine,  and  meerschaum. 
Its  soluble  salts  are  widely  distributed  in  mineral  waters. 

Carnallite  is  a  double  chloride  of  magnesium  and 
potassium,  found  in  large  quantities  at  Stassfurth. 

429.  The   metal   magnesium   is  obtained  by  fusing  its 
chloride    with    sodium  :    MgCl2  -f  2Xa  =  2XaCl  -}-  Mg. 
It  is  a  silver-white  metal,  which  burns  in   the  air  with 
a  white  flame  of  dazzling  brilliancy.     This  flame  contains 
enough   of  the   actinic  rays   to   render  it  serviceable  as 
an  artificial  light  in  photography. 

430.  Magnesium    oxide,    MgO    (calcined    magnesia],    is 
formed  when   magnesium    is   burned   in   the   air,  but  is 


COMPOUNDS  OF  MAGNESIUM.  227 

generally  prepared  by  roasting  the  carbonate.  It  is  a 
white,  bulky,  infusible  powder,  almost  insoluble  in  water, 
and  yet  capable,  when  moistened,  of  bluing  red  litmus, 
forming  magnesium  hydrate.  It  gradually  changes  in 
the  air  to  magnesium  carbonate. 

431.  Magnesium  carbonate,  MgCO3.    The  magnesia  alba 
of  the  druggist  is  a  mixture  of  magnesium  carbonate  and 
magnesium  hydrate.     It   is   prepared  by  adding  sodium 
carbonate   to   a   boiling    solution    of  a   magnesium    salt, 
and  washing  the  resulting  precipitate.     Both  the   oxide 
and  carbonate  are  used  in  medicine  as  antacids. 

432.  Magnesium  chloride,  MgCl2,  is  formed  when  hy- 
drochloric acid  is  added  to  either  of  the  preceding  com- 
pounds.   Like  calcium  chloride,  it  crystallizes  with  6II2O, 
and  is  deliquescent.     It  can  not  be  deprived  of  its  water 
of  crystallization  without  decomposition.    The  anhydrous 
salt  is  prepared  by  igniting  the  double  chloride  of  mag- 
nesium and  ammonium  :  MgCl2  +  NH4C1  -j-  6H2O.    This 
first  loses  its  water  of  crystallization ;    then   the   ammo- 
nium chloride   and   the  anhydrous  magnesium   chloride 
remain. 

433.  Magnesium    sulphate,    MgSO4  -j-  7H2O    (Epsom 
salts'),  is   a   common    constituent  of  mineral   waters.     It 
is  prepared  in  considerable  quantities  from  the  "  bittern  " 
of  sea  waters,  which  remains  after  the  sodium  chloride 
has  crystallized  out ;  and  also  from  the  native  carbonate,' 
by  treating  either  with    sulphuric    acid.     It   is   a   very 
soluble    salt,    but   crystallizes    from    strong    solutions   in 
monoclinic  prisms  containing  seven  molecules  of  water. 
Six  of  these   molecules   are   easily   driven    off  by    heat, 
but  the   seventh  is  retained  even  at  200°  C.     This  last 
atom    is   the   "water   of  constitution,"   and   may  be  re- 
placed by  various  sulphates  of  other  metals,  giving  rise 
to  double  salts  with  six  molecules  of  water ;  as, 

MgS04-f  K2S04  +  6H20. 


228 


CHEMISTRY. 


434.  All   the   soluble   salts  of  magnesia  have  an  un- 
pleasant, bitter  taste,   but  many   of  them    are    used    in 
medicine  as  cathartics.     All  the  compounds  of  magnesia 
show   a   strong   tendency  to   combine  with    the  salts  of 
ammonia,  and  form  double  salts  which  are  easily  soluble 
in  water.     Hence,  the    addition  of  ammonium  salts  will 
very  generally  hinder   the   precipitation    of  magnesium 
by  the  ordinary  reagents.     An  exception  to  this  is  found 
in  magnesium  phosphate. 

435.  Magnesium  phosphate,  MgHPO4  -f  7II2O,  forms 
when  sodium  di-phosphate  is  added  to  a  magnesium  salt. 
If  an  ammonium  salt  is  present,  a  difficultly  soluble  pre- 
cipitate of  the  formula  MgNH4PO4  -f  GH2O  crystallizes 
out.     When    this  salt  is  dried  and  then  ignited,  it  first 
loses  its  water,  then  its  ammonia,  and  becomes  changed 
to  magnesium  pyrophosphate  : 


This   is    the    form   in  which   magnesia  is  generally  esti 
mated  in  quantitative  analysis. 


ZINC. 


436.  Zinc  occurs  in  nature  chiefly  as  a  sulphide 
(blende),  or  as  a  carbonate  (Smith- 
sonite).  It  also  occurs  as  an  oxide 
(red  zinc  ore),  and  as  a  silicate  (cal- 
ami ne). 

In  preparing  the  metal,  (1)  the  ores  are 
roasted  in  air,  whereby  they  are  converted 
to  zinc  oxide.  (2)  This  oxide  is  then  mixed 
with  powdered  coke  and  heated  in  earthen 
crucibles.  At  white  heat  the  metal  is  re- 
duced, and,  volatilizing,  is  condensed  in  suit- 
able receivers:  ZnO  -f  C  =  (X)  -f  Zn. 

FIG.  90.  437.  Zinc  is  a  bluish-white  metal. 


ZINC.  229 

It  is  quite  malleable  between  100°  C.  and  150°  C.,  and 
between  these  temperatures  is  readily  rolled  into  sheets. 
Very  curiously,  it  is  brittle  both  below  and  above  these 
temperatures,  and,  in  thick  plates,  breaks  with  a  crys- 
talline fracture.  When  exposed  to  the  air,  zinc  soon 
tarnishes,  forming  a  closely  adhering  film  of  oxide, 
which  prevents  it  from  further  change.  This  property 
is  utilized  in  the  so-called  galvanized  iron,  which  is 
iron  coated  with  zinc,  to  prevent  the  iron  from  rusting. 
Zinc  is  easily  soluble  in  most  acids  and  in  boiling 
caustic  alkalies,  with  evolution  of  hydrogen. 

(1)  H2SO4  +  Zn  =  ZnSO4  +  fl2. 

(2)  2KHO  +  Zn  =  K2ZnO2  +  #2. 

In  both  these  cases  the  action  is  accelerated  by  the 
presence  of  another  metal,  as  a  coil  of  platinum  wire. 

Zinc  is  used  as  the  electro-positive  metal  in  most  gal- 
vanic batteries,  and  in  the  form  of  sheets  for  roofing 
and  other  purposes. 

438.  Zinc  chloride,  ZnCl2,  is  formed  when  zinc  is  dis- 
solved  in  hydrochloric  acid.     The  solution  is  used  as  a 
disinfectant  and  in  soldering.     On  evaporating  the  solu- 
tion to  dryness,  a  white,  deliquescent   salt   is   obtained, 
which  absorbs  water  greedily,  and  is  sometimes  used  in 
surgery  as  a  caustic. 

439.  Zinc   hydrate,    Zn(HO)2,    is   formed    when    any 
alkali  is  cautiously  added  to  a  solution   of  a   zinc   salt. 
It   is    easily    soluble    in    an    excess    of  the    precipitant. 
When    dried,    it    is   readily    decomposed    by    heat    into 
zinc  oxide,  ZnO.    This  body  is  usually  prepared  by  burn- 
ing  zinc    in    a    current   of  air.     It   is   a   light   powder, 
yellow  when  hot  and  white  when  cold,  and  extensively 
used  as  a  paint,  under  the  name  of  "  zinc  white." 

440.  Zinc  sulphate,  ZnSO4  4-  7H2O,  may  be  obtained 
by  evaporating  a  solution   of  zinc  in  sulphuric  acid,  as 


230  CHEMISTRY. 

colorless  prisms,  isomorphous  with  magnesium  sulphate, 
which  it  strongly  resembles.  It  also  forms  double  salts 
with  6H2O;  as,  ZnSO4  +  K2SO4  +  6H2O.  It  is  used 
in  medicine,  and  produces  vomiting  when  swallowed 
in  even  moderate  doses. 

441.  Zinc   carbona'te   occurs   native.     The    precipitate 
which  forms  when  an  alkaline  carbonate   is  added  to  a 
zinc    solution    always   contains   zinc    hydrate,    and    is   a 
basic    carbonate,    although    its    composition    varies    with 
the  mode  of  preparation,  e.  g.,  2ZnCO8  +  3Zn(HO)2. 

442.  Zinc   sulphide,   ZnS,   is   formed    when   zinc   salts 
are    decomposed    by   ammonium    sulphide.     It   is   easily 
soluble  in  dilute  acids  (excepting  acetic),  and  is  readily 
oxidized  when   heated  in  air.     It    is    the    only  insoluble 
white  sulphide  formed  in  the  wet  way,  and  hence   is   a 
characteristic  test  for  zinc. 

443.  Zinc  alloys  are   numerous  and  important.     Brass 
contains  about  one  part  of  zinc  to  two  of  copper.    Ger- 
man   silver    contains,    in    addition,    one    part    of   nickel. 
Many  varieties  of  bronze  also  contain  zinc. 

CADMIUM. 

444.  Cadmium  is  found  in  small  quantities,  associated 
with   zinc   ores.     Being    more    volatile    than    zinc,    it    is 
obtained  from  the  first  portions  of  Uic  distillate  in  zinc 
smelting. 

It  is  a  soft,  white,  easily  fusible,  and  volatile  metal. 
It  burns  somewhat  readily  in  air,  forming  a  brown 
oxide,  CdO.  The  metal  is  used  to  form  alloys,  which 
fuse  at  very  low  temperatures.  An  alloy  8  parts  of 
lead,  15  of  bismuth,  4  of  tin,  and  3  of  cadmium,  melts 
at  60°  C.  (Wood's  metal). 

Its  sulphide  is  used  in  water-colors  as  a  yellow  pig- 
ment. Cadmium  iodide  is  used  by  photographers. 


RARE  DYAD  METALS.  231 


Tests  for  the  Magnesium  Group. 

445.  In  analytical  chemistry,  these  metals  are  placed 
in   three   different  groups,   because   of  the   behavior   of 
their  sulphides. 

I.  (a)  In  acid  solutions,  sulphuretted  hydrogen  precipitates  cad- 
mium only  as  a  characteristic,  yellow,  amorphous  powder,  insoluble 
in  dilute  acids,     (b)  In  neutral  or  alkaline  solutions  it  precipitates 
white   zinc   sulphide,  which    is   soluble    in    all   dilute  acids,  except 
acetic,     (c)  Magnesium  does  not  form    a  sulphide  in  the  wet  way. 
If  a  solution  containing  these  three  elements  has  been  treated  suc- 
cessively with  sulphuretted  hydrogen,  and   ammonium   sulphide   is 
mixed  with  sodium  di-phosphate,  white  MgNH4PO4  precipitates. 

II.  The   fixed   alkalies    precipitate   all    these   elements   as   white 
hydrates.     Zinc  hydrate  alone  is  soluble  in  potash  and  soda. 

III.  The    alkaline    carbonates   produce    white    basic    carbonates. 
The  presence  of  ammoniacal  salts  either  hinders  (Cd)   or   prevents 
(Mg,  Zn)  the  formation  of  this  precipitate. 

IV.  Heated   before   the   blowpipe   on    charcoal,    (a)    magnesium 
oxide    becomes    intensely   luminous;    the    residue,    moistened    with 
cobalt   solution   and   reheated,  yields  a  pink  mass,     (b)  Zinc  oxide 
becomes  yellow  while  hot,  and  again  white  on  cooling.     Moistened 
with  cobalt  solution  and  reheated,  it  forms  a  green  mass,     (c)  Cad- 
mium oxide,  when  anhydrous,  is  a  brown  powder. 

446.  Rare   dyad   metals.     To  this  group   are   usually 
referred  a  number  of  rare  metals  which  have  not  been 
thoroughly  classified.    Some  of  these  are,  perhaps,  triads, 
as  their  oxides  resemble  alumina.    They  have  been  found 
only  in  a  few  rare  minerals,  principally  obtained  in  the 
Scandinavian    peninsula. 

They  are  glucinum ;  thorinum,  yttrium,  and  erbium; 
lanthanum  and  didymium ;  cerium  and  terbium. 

Cerium  only  has  received  any  practical  application. 
Some  of  its  salts  have  been  used  in  medicine  in  various 
dyspeptic  conditions  of  the  stomach. 

447.  Mercury  and  copper  are  metals  not  easily  classi- 
fied.    They  form  two  series  of  compounds :    (1)  ic  salts, 


232 


CHEMISTRY. 


in  which  they  act  as  dyad  elements,  as  HgCl2,  mercuric 
chloride,  and  CuCl2,  cupric  chloride;  (2)  ous  salts,  in 
which  they  are  apparently  monad  elements,  as  HgCl, 
mercurous  chloride,  and  CuCl,  cuprous  chloride. 

Theoretically,  it  is  better  to  consider  that  these  ele- 
ments are  always  divalent,  and  that  their  ous  salts 
contain  a  double  atom  of  the  metal  whose  affinities 
partially  satisfy  each  other.  Thus  the  theoretical  for- 
mula of  mercurous  chloride  is  Hg2Cl2,  and  of  cuprous 
chloride,  Cu2Cl2.  These  may  be  represented  graphically 
thus : 

Hg— Cl  Cu— Cl 


L- 


g-Cl 


I 

Cu— Cl 


The  ous  salts  of  both  resemble  those  of  silver;  the  ic 
salts  resemble  those  of  the  dyad  group. 

MERCURY. 

448.  Mercury  is  not  widely  distributed.  It  occurs, 
however,  in  considerable  quantities  in  a  few  localities, 
of  which  the  best  known  are  Idria,  in  Austria;  Almaden, 
in  Spain;  and  New  Almaden,  in  California.  The  metal 
sometimes  occurs  native,  but  its  principal  ore  is  the 
sulphide  IlgS  (cinnabar),  from  which  it  is  generally 
extracted. 

The  process  is  very  sim- 
ple.    The  sulphide  heated 
in    air   easily  decomposes, 
yielding  sulphurous  anhy- 
dride and  mercury: 
HgS  +  02  =  S02  +  Hg. 
Sometimes  lime  is  added. 
The    mercury    volatilizes 
and  is  conducted  through 
earthen   pipes,  called  alu- 

dels.     The   mercury  which   escapes   condensation   in  the   aludels  is 
condensed  in  large  brick  chambers. 


FIG.  91. 


MERCURY.  233 

449.  Mercury  is  the   only   metal   which   is   liquid   at 
ordinary  temperatures.     It   is   largely  used  in  the   con- 
struction of  barometers,  and  in  apparatus  for  the  meas- 
urement  of  gases.     It   is    the    most  available   liquid  in 
the   construction   of  thermometers,    because    it    expands 
regularly,   on  being  heated,   from    0°  C.  to  100°  C.     It 
is    solid    at    --40°    C. ;     volatilizes    at    all    temperatures 
above  10°  C. ;    and  boils  at  360°  C.,  yielding  a  colorless 
vapor    100    times   as   dense   as   hydrogen.      It    possesses 
a   bright,   grayish-white    luster,    which    is    scarcely   tar- 
nished on  exposure  to  the  air.     Heated  for  a  long  time 
in   air,   it    forms    the    red    oxide,    HgO.     It   enters   into 
combination  with  chlorine,  bromine,  iodine,  and  sulphur 
at  ordinary  temperatures.     It  decomposes  strong  boiling 
sulphuric  acid,  forming  mercuric  sulphate ;    but  its  best 
solvent   is    nitric   acid.     With    this   it   forms    mercurous 
nitrate,   Hg2(NO3)2,  and   mercuric  nitrate,   Hg(NO3)2, 
besides  a  large  number  of  basic  salts. 

450.  Mercury  forms  two  series  of  compounds  as  unlike 
in  their  properties  as  if  they  had  been  formed  from  two 
different  elements.     The  first  series,  typified  by  corrosive 
sublimate,  HgCl2,  is  the  mercuric  series;  the  other  series, 
which    is   typified   by    calomel,  HgCl  or  Hg2Cl2,   is  the 
mercurous  series. 

The  mercurous  compounds  are  frequently  written  with 
half  their  molecular  formula? ;  thus,  mercurous  chloride, 
or  calomel,  is  represented  either  by  Hg2Cl2  or  by 
HgCl. 

451.  The    mercurous   salts    are    readily    converted    by 
oxidizing  agents  to  mercuric  compounds;    and  the  mer- 
curic compounds  as  easily  converted  by  reducing  agents 
to  mercurous  compounds. 

All  compounds  of  mercury,  and  even  the  vapor  of 
mercury,  have  a  decided  action  when  taken  in  any  way 
into  the  human  system ;  producing,  in  excess,  a  dis- 


234  CHEMISTRY. 

agreeable  and  sometimes  dangerous  salivation.  It  is, 
however,  curious  to  note  that  the  mercuric  compounds 
are  more  energetic  in  their  action,  and  are  deadly 
poisons.  The  mercurous  compounds  are  milder,  and 
are  more  frequently  used  in  medicine. 

Hg- 

MERCUROUS  SERIES, 

frg- 

452.  Mercurous  nitrate,  Hg2(NO3)2,  forms  when  mer- 
cury is  digested  in  an  excess  of  cold,  dilute,  nitric  acid. 
Basic    salts    form    when    the    mercury   is   in   excess,  and 
mercuric    salts,   in    warm    solutions    or    in    strong    nitric 
acid.     Mercurous  nitrate  forms  colorless  tables,  partially 
decomposed  by  water,  but  soluble  in  water  acidified  by 
nitric  acid.     It  is  advisable  always  to  add  to  this  solu- 
tion a  little  metallic  mercury,  to  prevent  the  formation 
of  mercuric  salts. 

453.  Mercurous   oxide,   Hg2O,    is   a   black,  amorphous 
powder,  obtained  by  adding  sodium  hydrate  to   a    solu- 
tion   of  mercurous    nitrate.     It    is    decomposed   by   heat 
and  light  into  Ilg  and  HgO. 

454.  Mercurous    chloride,    IIg2012,    or    calomel,    is    a 
white,  amorphous  powder,  insoluble  in  water  and  dilute 
acids,  which    may   be   obtained   by  adding   hydrochloric 
acid  to  mercurous  nitrate. 

Commercially,  it  is  made  by  subliming  (1)  a  mixture  of  mercuric 
chloride  and  mercury,  or  (2)  u  mixture  of  mercuric  sulphate,  mer- 
cury, and  common  salt:  HgSO4-f  Hg+ 2NaCl=  Na2SO4-f  Hg2Cl2. 
The  vapor  is  condensed  in  large  chambers,  and  is  then  ground  to 
a  powder  and  washed  with  water.  Sodium  hydrate  decomposes  it, 
yielding  black  mercurous  oxide. 

455.  Mercurous   iodide,   Hg2I2,    is    a   greenish   yellow 
powder,    obtained    by    mixing    solutions    of    mercurous 
nitrate  and  potassium  iodide.     It  is  insoluble  in  alcohol. 


MERCURIC  SERIES.  235 

MERCURIC  SERIES,  Hg". 

456.  Mercuric  oxide,  HgO.     This  has  two  forms:    (1) 
the  red  oxide,  which    is   prepared   by   heating   mercury 
for   several    days    in    air    at   about   450°  C. ;    and  (2)    a 
yellow  oxide,  by  adding  potassium  hydrate  to  a  solution 
of  mercuric  salts.     The  yellow  oxide  is  more  susceptible 
of  chemical  change,  which  is  perhaps  due  to   the   more 
finely  divided   state   of  the   precipitated   oxide.     Either 
of  these  forms,  on  being  heated,  takes  on  a  darker  color, 
and,  at  G30°  C.,  decomposes  into  oxygen  and  mercury. 
The  residue,  if  any,  becomes  red  on  cooling. 

457.  Mercuric  nitrate,  Hg(NO3)2,  is  best  prepared  by 
dissolving    mercuric    oxide   in    an    excess   of  nitric  acid. 
It  crystallizes   in   small  needles,  which   arc    decomposed 
by  heat,  leaving  the  red  oxide. 

458.  Mercuric    chloride,    HgCl2    (corrosive    sublimate). 
This  important  salt  is  obtained  usually  by  subliming  a 
mixture  of  mercuric  sulphate  with  common  salt : 

HgS04  +  2NaCl  =  Na2SO4  +  HgCl2 ; 

for  laboratory  purposes,  by  dissolving  mercury  in  aqua 
regia.  It  is  easily  soluble  in  water  and  in  alcohol,  and, 
on  crystallizing,  forms  rhombohedral  prisms  which  melt 
at  270°  C.,  and  sublime  unchanged  at  300°  C.  Its  so^ 
lution  has  a  sharp,  metallic  taste,  and  is  an  active 
poison.  It  coagulates  albumin,  forming  with  it  insoluble 
"  albuminates."  Hence,  it  has  been  largely  used  as  an 
antiseptic  in  preserving  animal  and  vegetable  tissues 
from  decay;  and  hence,  also,  albumin  is  an  excellent 
antidote  in  cases  of  poisoning  by  corrosive  sublimate. 

459.  Mercuric  iodide,  HgI2>  is  formed  when  potassium 
iodide    is  added    to    a    solution   of  mercuric  salts.     It  is 
first  salmon-colored,  but  changes  to  a  beautiful  red  pre- 
cipitate, which  is  insoluble  in  water.    An  excess  of  either 


236  CHEMISTRY. 

reagent  must  be  avoided,  because  very  soluble  double 
salts  are  formed,  such  as  IIgI2KI  or  HgI22HgCl2.  If 
the  red  iodide  is  heated,  it  sublimes  in  yellow,  prismatic 
crystals,  which  slowly  revert  to  red  octahedra  if  left  un- 
touched, and  immediately  when  rubbed  with  any  hard 
substance.  It  therefore  exhibits  a  remarkable  example 
of  dimorphism. 

460.  Mercuric    sulphide,    IlgS,    occurs    in    nature    as 
cinnabar.     The    artificial    sulphide,    formed    by    precipi- 
tating   mercuric    salts  with    sulphuretted  hydrogen,  is  a 
black,  amorphous  powder.     When  this   sulphide   is  sub- 
limed, or  when    mercury  is  sublimed  at  a  low  red  heat 
with  one-sixth  of  its  weight  of  sulphur,  a  beautiful  red 
sulphide    forms,    which    is    the    pigment    known    as    ver- 
million. 

461.  Ammonium   compounds   of  mercury    are    formed 
when  ammonia  or  its  salts  act  upon  the   compounds  of 
mercury.     They  may  be   regarded  as  derived  from  am- 
monium, in  which  two  atoms  of  hydrogen  are  replaced 
by   a   double    mercurous    atom   (NrII2IIg/2)',  or  by  the 
mercuric  atom  (NFII2IIg")'.    In  either  case,  a  monatomic 
radical    is    formed,  which    may  combine  with  any  nega- 
tive   monatomic    radical ;    or,    in    multiple    forms,    with 
dyads,  triads,  etc.    These  compounds  are  very  numerous. 

Among  the  most  important  are: 

(1)  Di-mercurosum-chloride  (NH2Hg2Cl),  which  forms  as  a  black 
powder  when  calomel  is  treated  with  aqua  ammonia,  and  becomes 
gray  upon  drying: 

Hg2Cl2  +  2  NH4,  HO  =  NH2Hg2Cl  +  NH4C1  -f  2H2O. 

-y- 

(2)  Mercuric  ammonium  chloride  (NH2HgCl),  commonly  known 
as  "  white  precipitate,"  which  forms  when   an    excess   of  aqua  am- 
monia is  added  to  a  solution  of  mercuric  chloride: 

HgCl2  +  2NH4,  HO  =  NH4C1  -f  2  H2O  -f  NH2HgCl. 
When    the    mercuric   chloride    is    in    excess,    a    double   salt    forms, 


COPPER.  237 

NH2HgCl -f- HgCl2;    but,    if  ammonium   chloride   is    in    excess,    a 
"fusible  white  precipitate,"  NH2HgCl  +  NH4C1. 

In  like  manner,  iodides,  bromides,  nitrates,  sulphates,  etc.,  may 
be  formed,  containing  either  NH2Hg2  or  NH2Hg/x  as  the  positive 
radical. 

462,  The  alloys  of  mercury  are  called  amalgams.    The 
metals  of  the  alkalies,  gold,   silver,  zinc,  tin,   lead,  and 
bismuth     dissolve    readily    in    an    excess    of    mercury. 
When    the    excess    of  mercury   is  removed,  these  amal- 
gams are  frequently  solid,  and  have  received  important 
applications    in    the   arts.     Sodium  amalgam  is  used  for 
extracting  gold  and  silver  from  their  ores;  tin  amalgam 
is  used  for  silvering   mirrors;    an    amalgam    of  tin   and 
silver,  for  plugging  hollow  teeth. 

TESTS. — (1)  All  solid  compounds  of  mercury  yield,  when  mixed 
with  dry  sodium  carbonate  and  heated  in  a  test  tube  of  hard  glass, 
globules  of  metallic  mercury. 

(2)  Solutions    of  the   salts   of  mercury   are   reduced   by  copper, 
forming  upon  it  a  white  metallic  coating,  with  a  greasy  feel. 

(3)  Mercurous  compounds  give  black  precipitates  with  the  alka- 
lies   and    with    sulphuretted   hydrogen;    with    hydrochloric   acid,    a 
white  precipitate  of  calomel. 

(4)  Mercuric   compounds   give,  with   caustic  soda   or   potash,    a 
yellow  precipitate;  with  sulphuretted  hydrogen,  a  black  precipitate 
(at  first  white);  with  potassium  iodide,  a  red  precipitate. 

COPPER. 

463,  Copper  sometimes  occurs  native,  generally  massive, 
"but,  at  times,  in  octahedral  crystals.     More  frequently  it 
is  found  as  a  sub-oxide   (red  copper  ore),    or   as   a   car- 
bonate   (malachite).     Its    principal    ore    is   the    sulphide 
(copper  pyrites),   although    this    is    seldom    found   pure, 
being  largely  associated  with  iron,  and  frequently  with 
other  elements,  as  arsenic  and  antimony. 

464,  The   preparation  of  copper  from  its  native  form 
or    from    its    oxygen    compounds    requires    merely    the 


238  CHEMISTRY. 

smelting  of  the  ore  with  coal.     The  reduction  of  copper 
from  the  sulphide  is  a  more  complex  process. 

(1)  The  ore  is  first  roasted  in  a  reverbatory  furnace  (Fig.  80), 
whereby  certain  constituents  (As,  Sb,  S)  are  volatilized,  and  others 
oxidized  (FeS2  to  Fe2O3).  (2)  This  product  is  roasted  with  a 
mixture  of  coal  and  silicates,  to  produce  a  soluble  slag  with  the 
iron,  while  the  copper  accumulates  as  a  nearly  pure  sub-sulphide 
(Cu2S).  (3)  When  the  iron  has  been  removed  by  a  succession  of 
these  operations,  the  heat  is  raised  and  a  portion  of  the  copper  is 
oxidized  and  reacts  upon  the  remaining  sub-sulphide  (2CuO-f- 
Cu2S  =  St>2  +  4  Cu),  yielding  metallic  copper.  (4)  The  final  stage 
of  the  process  consists  in  stirring  up  the  melted  mass  with  a  long 
stick  of  green  wood,  which  reduces  the  last  portions  of  the  oxide. 
The  metal  is  then  drawn  off  and  cast  into  ingots. 

465.  Copper  is  a  reddish  metal,  very  malleable,  ductile, 
and  tenacious,  and  is  one  of  the  best  conductors  of  heat 
and    electricity.      It    preserves    its    brilliant    luster    un- 
changed   in    dry    air,    unless    heated,    when    it    oxidizes 
rapidly,    forming    a    many-colored    film,    which    finally 
changes   to   scales   of  the   black  oxide.     In  moist  air  it 
becomes  dull  looking,  and  slowly  forms  a  crust  of  green 
basic  carbonate.     This  change  takes  place  more  rapidly 
in    the    presence    of  acid  vapors,  or  when  the  copper  is 
moistened  with  ammonia  or  with  solutions  of  chlorides. 

466.  It  is  a  dyad  which  differs  from  all  those  previ- 
ously studied  in  its  high  melting  point  (1200°  C.),  and 
in  the  fact  that  it  is  only  slightly  volatile,  even  at  very 
high  temperatures.     It   resembles    mercury   in    some    of 
its   properties:    (1)    in    that    it    is    hardly    attacked    by 
hydrochloric  or  sulphuric  acid,  except  when  heated,  but 
readily  dissolves   in    dilute    nitric   acid ;    (2)  by  forming 
ammonium    compounds  in  which  the  copper  apparently 
replaces  a  part  of  the   hydrogen   of  the   ammonium,  as 
2NH3,  CuCl2 ;    and  (3)  in  forming  two  series  of  salts  — 
the  cuprous,  typified  by  cuprous  chloride  (Cu2Cl2),  and 
the    cupric,   typified    by   cupric   chloride    (CuCl2>,     The 


COMPOUNDS  OF  COPPER.  239 

latter   series   is   by  far  the   most  abundant   and   impor- 
tant of  the  copper  compounds. 

467.  Cuprous  chloride,  Cu2Cl2,  is  best  made  by  digest- 
ing for  some  time  a  mixture  of  copper  filings  and  cupric 
oxide   in    hydrochloric   acid.     The  salt  is  soluble  in  hy- 
drochloric  acid ;    but,  when    the  solution  is  poured  into 
a  large  quantity  of  water,  it  separates  .out   as   a   white 
crystalline  powder. 

468.  Cuprous  oxide,  Cu2O,  is  obtained  when  a  solution 
containing,  cupric  sulphate,  grape  sugar,  and    an    excess 
of   sodium    hydrate,    is    warmed.      Generally,    a   yellow 
cuprous    hydrate,   Cu2O,  H2O,   first  separates   out;    but, 
on    longer    boiling,    anhydrous    red    cuprous    oxide    is 
formed.     This   reaction    is   facilitated   by  a  considerable 
addition    of  tartaric    acid.     The    red    oxide    is    used   to 
impart  a  beautiful  ruby  color  to  glass. 

Most  oxy-acids  decompose  this  oxide,  precipitating 
metallic  copper  and  forming  cupric  salts. 

469.  Cupric  oxide,  CuO,  may  be  prepared  by  roasting 
copper  in  air  or  by  igniting  the  nitrate.    When  sodium 
hydrate    is    added    in    excess    to  a  solution  of  a  cupric 
salt,    a    pale    blue    precipitate    forms,    which    is    cupric 
hydrate,  Cu(HO)2;    but,  upon   heating  the  mixture,  the 
black  anhydrous  oxide   forms,  even   in   the  presence  of 
water.     It   is   easily  reduced,  especially  in   the  presence 
of  hydrocarbons,  for  which  reason  it  is  extensively  used 
as  an  oxidizing  agent  in  organic  analyses. 

Combined  with  oxy-acids,  it  forms  a  large  series  of 
salts,  which  are  all  white  when  anhydrous,  and  blue  or 
greenish  when  hydrated. 

470.  The  native  sulphide,  CuS,  has  already  been  men- 
tioned   as    one    of  the  chief   sources    of  copper.      It    is 
formed    artificially    as    a    black    precipitate    when    sul- 
phuretted hydrogen   is  added  to  cupric  solutions.     It  is 
readily  oxidizable  in  air,  forming  cupric  sulphate. 


240  CHEMISTRY. 

471.  Cupric  sulphate,  CuSO4  -f  5H2O  (blue  vitriol*},  is 
the  most  important  salt.     It  is  obtained  on  boiling  cop- 
per in  strong  sulphuric  acid,  as  blue  triclinic  prisms: 

Cu  +  2II2S04  =  CuS04  +  2H20  -f  S02. 

These  crystals  are  changed  to  a  white  anhydrous  powder 
at  about  200°  C.,  which  absorb  water  greedily,  and 
again  become  blue.  Hence,  it  is  used  to  remove  the 
last  portions  of  water  from  alcohols,  ethers,  etc.  Al- 
though it  contains  but  5II2O,  it  forms  with  alkaline 
sulphates  double  salts  containing  6H2O,  and  therefore 
analogous,  as  they  are  isomorphous  with  magnesium 
double  sulphates;  e.  g.,  K2,  Cu(SO4)2  -f  GII2O.  With 
an  excess  of  aqua  ammonia,  it  forms  an  exceedingly 
soluble  blue  compound  (4XII3,  H2O,  CuSO4),  which, 
upon  being  dried  and  heated  to  150°  C.,  becomes  cu- 
pric-ammonium  sulphate,  2NH3,  CuSO4. 

472.  Cupric  nitrate,  Cu(XO3)2,  is  made  by  dissolving 
copper    in    nitric    acid.      On    evaporating,    bright    blue 
crystals   form,  which    are   very   deliquescent    and    easily 
decomposed  by  heat,  leaving  cupric  oxide. 

473.  Numerous   carbonates  of  copper  occur  in  nature. 
The    most   prized    of  these   is   malachite,  which  takes  a 
high  polish  and  is  used  for  ornaments.    A  similar  com- 
pound  forms  when  sodium  carbonate  is  added  to  a  hot 
solution  of  a  cupric  salt,  CuCO3  -f-  Cu(HO)2. 

474.  The   uses  of  copper  in  the  arts  are  well  known ; 
but,  perhaps,  its  alloys  are  more  extensively  used   than 
the    metal    itself.     Gun    metal,    bell    metal,    bronze,    and 
speculum  metal  are  alloys  with  tin,  containing  from  66 

\  to  90  per  cent  of  copper.  They  are  distinguished  by 
great  hardness,  and  a  susceptibility  of  taking  on  a  high 
polish.  Copper  is  also  a  constituent  of  brass,  German 
silver,  most  alloys  of  silver,  and  of  "  red  "  gold. 

The    sulphate   of  copper    is    largely  used    in   galvanic 


THE  DYAD  GROUP.  241 

batteries  and  in  electrotyping.  Some  of  the  salts  of 
copper  are  valuable  pigments.  Brunswick  green  is  an 
oxy-chloride.  Scheele's,  or  Paris,  green  and  Schweinfurt 
green  are  arsenites;  beautiful  greens,  but  very  poisonous. 
Verdigris  is  a  basic  acetate,  although  this  term  is  often 
incorrectly  applied  to  the  green  basic  carbonate  which 
forms  when  copper  is  exposed  to  moist  air. 

It  must  not  be  forgotten  that  all  soluble  salts  of  copper  are  active 
poisons.  Too  much  care  can  not  be  taken  to  keep  copper  vessels 
used  for  cooking  perfectly  bright  and  clean,  as  the  presence  of  oily 
matters  facilitates  the  solution  even  of  the  black  oxide.  Its  proper 
antidote  is  the  albumen  of  eggs. 

TESTS. — (1)  Ammonia,  added  to  any  cupric  solution,  produces  at 
first  a  greenish  blue  precipitate  which  dissolves  in  excess,  forming 
an  azure  blue  solution.  (2)  Potassium  ferrocyanide  gives  a  dark 
brown  precipitate  of  cupric  ferrocyanide.  (3)  Sulphuretted  hydro- 
gen, or  an  alkaline  sulphide,  forms  a  black  precipitate  insoluble  in 
dilute  acids  and  slightly  soluble  in  ammonia.  (4)  A  bright  slip  of 
iron  plunged  in  an  acid  solution  of  copper,  even  when  quite  dilute, 
becomes  soon  coated  with  the  red  metal.  (5)  See  §758. 

Recapitulation. 

Review  $  400,  401;  427;  447. 

These  dyad  elements  ma}*  be  arranged  with  the  monads  Li  and  Ag 
into  sub-groups,  as  follows: 


I 

Calcium,            40 
Strontium,        87.5 
Barium,           137 

II 

(Li.  7) 

III 

Copper,              63 
(Ag  108) 
Mercury,        200 
Lead,    "           207 

Magnesium,         24 
Zinc,                     65 
Cadmium,          112 

Lead,               204 

Their  carbonates  are  insoluble  in  H2O,  and  are  decomposed  by  heat, 

yielding  oxides. 
The   oxides    of  the    first   sub-group   resemble  those  of  the  alkalies, 

BaO  being  the  nearest. 
The  chlorides  of  the  first  and  second  sub-groups  are  all  soluble  in 

water,  and  most  are  deliquescent  bodies. 
The   protochlorides   of  the   third   sub-group  are  either  insoluble  in 

water  or  difficultly  soluble  (Pb  in  33  parts). 
Cbem.— 16. 


CHAPTEE    XIII. 

THE    TRIAD    METALS. 


j 

..  H 

o  > 
EH 

H 

ELEMENT. 

SYMBf 

ATOM 
WEKJl 

\l 

•J.  C 

MELT1 
POINT 

DISCOVERER. 

Indium 

In 

113.4 

7.4 

170° 

Reich  and  Richter,  1863. 

Gold 

Au 

107 

19.34 

1250° 

Thallium 

Tl 

204 

11.8 

285° 

Crookcs,      .     .     .     1861. 

475.  These  metals  have  few  properties  in  common, 
beyond  the  fact  that  they  are  triad  elements,  uniting 
with  three  atoms  of  chlorine  to  form  InCl3,  T1C13,  and 
AuCl3. 

Indium  and  thallium  are  very  rare.  The  principal 
interest  that  attaches  to  them  is  derived  from  the  fact 
that  they  were  recently  discovered  by  the  application 
of  the  spectrum  analysis.  The  spectrum  of  indium  con- 
tains two  bright  blue  bands.  It  occurs  in  some  ores 
of  zinc,  which  metal  it  very  much  resembles.  Thallium 
is  more  widely  distributed,  though  in  very  small  quan- 
tities. Its  principal  sources  are  certain  iron  and  copper 
pyrites.  In  its  physical  properties  it  resembles  lead; 
but,  in  its  chemical,  is  more  closely  allied  to  the  alka- 
lies, forming  a  caustic  hydrate,  T1HO,  and  to  silver, 
forming  an  insoluble  white  chloride,  T1C1. 
(242) 


GOLD.  243 

GOLD. 

476.  Gold  is  more  widely  distributed  than  is  generally 
supposed,   being    found    in    many    alluvial    sands    in   all 
parts   of  the   world.     Its    richest   deposits   are    in    Cali- 
fornia and  Australia.     It  is  generally  found   native,  but 
is   frequently  associated  with   ores   of  other   metals.     It 
is  obtained  (1)  by  simple  washing  in  a  stream  of  water, 
or  (2)  by  treating  the  crushed  ore  with  mercuiy,  which 
dissolves  out  the  gold.     The   resulting   amalgam   is   dis- 
tilled, the   mercury  is  recovered    for   future    operations, 
and  the  gold  which  remains  is  cast  into  bars. 

477.  Gold  is  a  yellow  metal,  of  high  specific  gravity, 
very   malleable   and   very   ductile.      When    obtained    in 
very  thin  sheets,  it  transmits   a   green    light.     It   is   so 
soft  that  pieces  of  pure  gold  foil  may  be  welded  together 
by  pressure,  as  in  dentistry.     The  gold  used  in  coins  or 
for  ornaments   is   hardened  by  being  alloyed  by  copper 
or  by  silver. 

An  ancient  commercial  method  of  measuring  the  fineness  of  gold 
still  obtains:  pure  gold  is  reckoned  at  24  carats;  and  the  alloys  are 
said  to  be  as  many  carats  fine  as  they  contain  parts  of  gold  in  24. 
Tbus,  the  best  jewellers'  gold  is  18  carats  fine,  and  contains  £f  of 
its  weight  in  gold.  One  U.  S.  gold  dollar  weighs  25.8  grains,  and 
contains  90  per  cent  of  gold  (21.6  carats  fine).  At  this  rate,  pure 
gold  is  $20.67  per  Troy  ounce.  British  coin  is  22  carats  fine. 

478.  Gold  is  not  acted  upon  by  air,  by  water,  or  by 
ordinary   acids.     It,   however,    dissolves   readily  in    any 
liquid  which   contains  free  chlorine.     Aqua  regia   is   its 
best  solvent,  yielding  auric  chloride. 

479.  Auric   chloride,   AuCl3,    on    evaporation   forms   a 
red  deliquescent  mass.    With  alkaline  chlorides  it  forms 
yellow,    needle-like    crystals;     as,    NaAuCl4   -(-  2  H2O. 
The    commercial    chloride  has  the  formula  AuCl3,  HC1. 
Heated  to  about  150°  C.,  it  partially  decomposes,  leaving 
aurous  chloride,  a  white  powder  insoluble  in  cold  water. 


244  CHEMISTRY. 

480.  Auric    oxide,    3H2O,  Au2O3,    forms    when    auric 
chloride    is    digested    with    magnesia.      It    possesses    no 
basic   properties,   but   rather   acts   as   a   weak   acid.     It 
dissolves  in  excess  of  potassium  hydrate,  and,  on  evap- 
orating, yields  yellow  needles:   K2O,  Au2O3 -f- 3H2O. 

Aurous  oxide,  Au2O,  acts  as  a  feeble  base.  Its  only 
important  salt  is  made  by  mixing  solutions  of  auric 
chloride  and  sodium  hyposulphite.  It  is  a  double  hypo- 
sulphite of  gold  and  sodium:  Na3Au,  2S2O3 -f  2H2O. 
It  is  used  by  photographers  in  "toning";  and,  very 
curiously,  neither  ferrous  sulphate  nor  stannous  chloride 
serves  to  detect  gold  in  its  solution. 

481.  The   uses   of  gold   in    coinage  and  in  ornaments 
have   been    known    through    all   ages  of  the  world.     In 
recent  times,  it   has   been    largely  employed  in  gilding, 
especially  by  the    application    of  galvanism.     The   gold 
is    usually    deposited    from    a    solution    of   the    cyanide, 
Au(CN)3,  and  may  be  obtained   in   any  required  thick- 
ness.    Gold,  in  its  finely  divided  state,  as  in  the  purple 
of  Cassius,  is  used  to  impart  a  ruby  color  to  glass,  and 
for  gilding  porcelain. 

TESTS. — (1)  All  gold  compounds  are  readily  reduced  to  metallic 
gold  by  heating. 

(2)  Gold   is   also  easily  reduced  in  solutions  not  containing  free 
nitric  acid  by  ferrous  sulphate,  by  oxalic  acid,  and  by  many  other 
reducing  agents  in  the  form  of  a  brown  powder. 

(3)  Stannous   chloride   produces   a   purple  precipitate  (purple  of 
Cassius),  which  is,  perhaps,  Au2O,  SnO,  SnO2. 


CHAP  TEE    XIV. 

THE    TETRAD    METALS. 


a 

o 

1 

w 

3 

ELEMENT. 

SYMBOL. 

ATOMIC  V 

O 
to 

DISCO  VF.RKR. 

Osmium 

Os 

199 

22.47  Tennant,       1803. 

Ruthenium 

Ru 

104.4 

11.4 

Klaus,            1844. 

Iridium 

Ir 

198 

21.1 

Tennant,       1803. 

Rhodium 

Rh 

104.4 

12. 

Wollaston,    1804. 

Platinum 

Pt 

197.5 

21.5 

Wood,           1741. 

Palladium 

Pd 

106.6 

11.8 

Wollaston,    1803. 

TRIAD   AND    MONAD    METALS. 

Gold 
Silver 

Au 

Ag 

197 
108 

19.3 
10.5 

f  Known  from 
*•  earliest  times. 

482.  These  metals  are  popularly  classed  together  as 
the  "  noble  metals."  They  possess  many  properties  in 
common,  viz :  a  remarkable  power  of  resisting  oxidation 
and  of  retaining  their  luster  unchanged  in  air;  a  high 
fusing  point ;  large  atomic  weights ;  and  high  specific 
gravities.  It  will  be  observed  that  in  the  table  they 
are  arranged  in  pairs.  The  two  members  of  each  more 
strongly  resemble  each  other  than  they  do  the  other 

(245) 


246  CHEMISTRY. 

members  of  the  group,  although  their  atomic  weights  and 
specific  gravities  bear  nearly  the  proportion  of  1  :  2. 

Gold  and  silver,  which  we  have  already  studied,  agree 
in  forming  an  insoluble  monad  chloride,  and  soluble 
double  salts  with  the  alkaline  chlorides.  They  differ  in 
their  fusing  points,  in  specific  gravity,  and  in  the  power 
of  resisting  oxidation.  Somewhat  similar  relations  and 
differences  are  found  in  the  other  pairs  of  the  group, 
especially  between  platinum  and  palladium ;  but  we 
must  not  attempt  to  form  a  strict  parallelism.  Iron  re- 
sembles osmium  because  of  its  acid  anhydride  FeO3 ;  and 
nickel,  palladium  because  it  has  but  one  basic  oxide. 

483.  The  first  six  metals  of  the  table  are  tetrad  metals, 
known  as  the  platinum  group.     Though  sometimes  found 
native,  these  more  frequently  occur  as  alloys  containing 
from  two  to  four  of  the  metals;    as,  for  example,  palla- 
dium   is   generally  found  with   platinum.     Iridium,  rho- 
dium,   and    osmium    also    occur    with    platinum ;    while 
iridosmine  (a  very  hard  mineral  used  for  the  points  of 
gold    pens)    generally  consists   of  iridium,  osmium,  rho- 
dium, and  ruthenium. 

484.  Osmium  and  ruthenium  are  white,  brittle  metals, 
nearly  or  quite  infusible  in  the  oxy-hydrogen  blowpipe. 
Nevertheless,    osmium    is   somewhat   volatile,    and    both 
differ  from  the  other  metals  of  this  group  in  combining 
with    oxygen    in    the    air  at   high   temperatures.     Their 
highest    oxides    are    OsO4,   RuO4,   which    are    the    only 
tetroxides    known,   and    are    neutral  bodies   of  offensive 
odor,   combining    neither   with    bases    nor   acids.     Their 
tri-oxides  act  as  acids.     They  form,  in   all,  five   oxides; 
as,  OsO,  Os2O3,  OsO2,  OsO3,  OsO4  ;  and  three  chlorides; 
as,  OsCl2,  Os2Cl6,  and  OsCl4.     These,  however,  are  not 
of  sufficient  importance  to  warrant  further  notice. 

485.  Iridium   and  rhodium   are   grayish-white  metals, 
hard  and  brittle,  and  with  difficulty  fused   in  the   oxy- 


THE  PLATINUM  GROUP.  247 

hydrogen  flame.  When  pure,  they  are  not  soluble,  even 
in  aqua  regia,  but  may  be  oxidized  by  fusion  with 
niter.  Iridium  forms  three  chlorides:  IrCl2,  Ir2Cl6, 
and  IrCl4.  Only  one  chloride  of  rhodium  is  known  — 
Eh2Cl6  ;  but  an  oxide,  RhO2,  is  known. 

486.  Platinum   and  palladium  are  the  most  abundant 
of  the    members   of  this   group.     They    are    also    more 
nearly  related,  being  both  brilliant  white  metals,  fusible 
only    in    the    oxy-hydrogen    flame,   quite   malleable   and 
ductile,    and    possessing    considerable    tenacity.      In    all 
these    respects    palladium    is    the    inferior    metal,  but   it 
surpasses  platinum  in  hardness. 

Both  form  two  chlorides:  PtCl2,  PtCl4,  and  PdCl2, 
PdCl4,  and  the  corresponding  oxides;  that  is,  they  act 
both  as  bivalent  and  quadrivalent  elements. 

487.  Palladium  is  the  only  metal  of  the  group  which 
is  soluble  in  HC1,  H2SO4,  and  in  HNO3.     The  nitrate, 
Pd(NO3)2,  is    used   for   the   quantitative    determination 
of  iodine,  forming,  when  added  to  solutions   of  iodides, 
a  black  precipitate  of  PdI2. 

488.  The  metal  palladium  possesses  the  curious  faculty 
of  absorbing,  or  "occluding,"  about  900  times  its  volume 
of  hydrogen.     This   product   is   sometimes   regarded    as 
an  alloy  of  palladium  with  hydrogen.     It  is  a  stronger 
reducing    agent    than    hydrogen    itself,    easily   reducing 
HgCl2  to  Hg2Cl2,  and  finally  to  Hg. 

489.  The  metal  platinum,  in  a   state  of  fine  division 
(spongy    platinum    or    platinum    black),    absorbs    more 
than    200    times    its   volume    of  oxygen,  and   then   acts 
as  a  strong  oxidizing  agent,  being  capable  of  converting 
alcohol  to  acetic  acid,  and   of  setting  on  fire  a  stream 
of  hydrogen. 

490.  Platinum  tetrachloride,  PtCl4,  is  the  only  impor- 
tant  salt   of  platinum.     It   is  obtained  as  a  yellow,  ex- 


248  CHEMISTRY. 

tremely  deliquescent  mass  when  platinum  is  dissolved 
in  aqua  regia.  Its  principal  use  is  to  form  double 
chlorides  with  alkaline  chlorides.  All  of  these,  except 
that  with  sodium,  are  difficultly  soluble  in  water  and 
alcohol.  Hence,  platinum  tetrachloride  is  a  valuable 
reagent  in  the  quantitative  determination  of  the  alka- 
lies, except  sodium. 

491.  The  double  chloride,  PtCl4,  2NII4C1,  when  heated 
to  redness,  is  entirely  decomposed,  yielding  the  "  spongy 

platinum  "  above  referred  to.  Platinum  black  is  platinum 
in  a  still  finer  state  of  division,  obtainable  by  heating 
a  mixture  of  solutions  of  sugar,  sodium  carbonate,  and 
platinum  tetrachloride.  It  is  used  as  a  coating  on  the 
silver  plate  in  Smee's  battery. 

492.  Platinum  is  the  only  metal  of  this  group  which 
has    received    any    extensive    applications    in    the    arts. 
It    is    especially    valuable    for   crucibles,    sulphuric    acid 
stills,  and    in    the  wires    used   for  electric  fuses.     It  was 
for  a  time  used  in  Russia  for  coins,  but  was  not   found 
convenient. 

TESTS. — (1)  All  dry  salts  of  the  platinum  group  arc  reduced  by 
heat  alone,  frequently  to  spongy  masses;  all  infusible,  except  by 
the  oxy-hydrogen  blowpipe. 

(2)  All  solutions  of  the  salts  of  these  metals  are  precipitated  as 
brown  or  black  sulphides  by  H2S.  Of  these  the  sulphides  of  plat- 
inum and  iridium  are  soluble  in  ammonium  sulphide. 


Recapitulation. 

The  noble  metals  are  difficultly  fusible,  and  are  not  easily  acted 
upon  by  acids. 

PtCl4  forms  difficultly  soluble  double  salts  with  most  of  the  alka- 
line chlorides. 

Ag,  Au,  and  Pt  alone  find  extensive  employment  in  the  arts. 


CHAPTER   XV. 


THE    IIEXAD    (JROUP    OF     METALS. 


% 

ELEMENT. 

SYMBOL. 

ATOMIC  WEIGHT. 

SPECIFIC  GRAVITY. 

DISCOVERER. 

Nickel 
Cobalt 

Ni 
Co 

58.7 
59 

8.82 

8.95 

Cronstedt,                         1751. 
Brandt,                               1733. 

Iron 
Manganese 

Fe 
Mn 

56 
55 

7.84 
8 

Scheele,                             1774. 

Chromium 
Aluminium 

Cr 
Al 

52.2 
27.4 

6.81 
2.G 

Vauquclin,                         1797. 
Woehler,                            1828. 

Gallium 

Ga 

69.9 

5.93 

Lecoq  de  Boisbaudran,  1876. 

Molybdenum 
Tungsten 

Mo 
W 

92 
184 

8.62 
17.6 

Hielm,                               1782. 
d'Elhujar,                         1781. 

Uranium 

u 

240. 

18.3 

Klaproth,                           1789. 

493.  Molybdenum  and  tungsten  resemble  each  other, 
but  differ  in  most  respects  from  the  remaining  metals 
given  in  the  table.  They  are  rare  elements  imperfectly 
studied,  and  are  probably  hcxad,  as  shown  by  the  chlo- 
rides, MoO2Cl2,WCl6,  and  the  anhydrides,  MoO8,WO8. 
They  also  form  a  variety  of  complex  products.  The 
only  compound  of  importance  is  ammonium  molybdate, 
(NH4)2O,  MoO3,  which  is  used  in  precipitating  phos- 
phoric and  arsenic  acids  from  acid  solutions. 

(249) 


250  CHEMISTRY. 

494,  Uranium  is  a  rare  metal  which,  in  its  analytical 
reactions,  somewhat  resembles  iron.     Its  nitrate  has  the 
formula  UO2(XO3)2,    and    is    a   yellow,  crystalline  salt, 
easily  soluble  in  water.     When  heated,  it  leaves  a  residue 
of  yellow  U2O3,  which,  when   further    ignited,  becomes 
brown    UO2.     When    treated    in    solution    with    sodium 
hydrate,  it  precipitates  as  uranium  hydrate,  UO2(OII)2, 
a  yellow  body  capable  of  acting  both  as  an  acid  and  as 
a  base.     The  group  (UO2)"  is  called  uranyl,  a  diatomic 
radical,  which  is  an   unusual  form.     This  radical  appears 
in  many  of  its  compounds,  as   rO2Cl2,  and  in  its  most 
usual    mineral,    UO2,2UO3.     Uranium    is    used    in    the 
determination    of    phosphorus    by    volumetric    analysis, 
forming  in  solutions  of  phosphoric  acid    salts   an   amor- 
phous yellow  precipitate,  insoluble  in  acetic  acid,  of  the 
formula  (UO2)"IIPO4  +  4  II2O.     The  oxides  of  uranium 
are  used  in  preparing  a  greenish  yellow  glass. 

495.  The    other  elements    given    in    the    table  are  fre- 
quently   classed    together    as   the    "  iron   group."     Those 
that   are    arranged    in    pairs  often  show  striking  resem- 
blances;   but    it    can    not    be    said    that    the   group  as  a 
whole  is  so  definitely  characterized  as   several    of  those 
which  have  been  already  studied. 

The  one  particular  in  which  they  all  agree  is  in  the 
formation  of  a  sesqui-oxide,  R2O3  ;  and  all  except  nickel 
have  the  corresponding  hexachloride,  U2C16.  If  we  admit 
the  double  atom  E2,  these  elements  are  tetratomic  or 
hexatomic, 

Fe-Cl3       Fe=Cl3  A1=C13       A1=C13 

as,       |  or  j'j  and  or  j!  , 

Fe=C\5       Fe=Cl3  A1-C13       A1-C13 

in  these  compounds.  Admitting  only  the  single  atom, 
and  writing  the  formula  A1C13,  they  are  apparently 
triad.  Some  chemists  prefer  to  reckon  aluminium  only 
as  a  triad,  since  it  forms  only  this  series  of  com- 


NICKEL  AND   COBALT.  251 

pounds.  Nevertheless,  it  is  closely  related  to  chromium 
and  to  iron.  Chromium  forms  an  undoubted  hexad, 
CrF6  ;  and  probably  in  the  higher  oxides,  CrO3,  FeO3, 
MnO3,  chromium,  iron,  and  manganese  are  hexads. 
With  the  exception  of  aluminium,  all  the  members  of 
the  group  also  act  as  dyads;  as,  NiCl2,  FeCl2.  Nickel 
forms  only  this  series  of  salts,  and  the  dyad  salts  of 
the  other  elements  are  quite  stable.  The  dyad  oxides 
are  all  strong  bases,  forming  salts  which  resemble  those 
of  zinc  and  magnesium,  with  which,  also,  they  are  iso- 
morphous,  and,  like  them,  form  double  sulphates  with 
the  alkalies;  as,  K2Fe(SO4)2  +  GH2O. 

496.  The  tetrad  oxides,  Fe2O3,  Cr2O3,  A12O3,  Mn2O3, 
are  wTeak  bases,  forming  with    alkalies  double  sulphates 
which  are  alums;  as,  A12O3,  3SO3  -f  K2O,  SO3  +  24H2O 
or  A1K(SO4)2  -f-  12II2O.     The  sesquioxide  of  aluminium 
acts  also  as  an  acid,  forming  with  the  alkalies  aluminates 
as,  K2O,  A12O3,  or  KA1O2. 

The  hexad  oxides  are  acid  anhydrides,  forming  salts 
like  K2O,  CrO3  and  K2O,  MnO3. 

£t  O  2t          /  O 

497.  It  will  be  noticed  that  in  the  table  on  page  192 
manganese  is  placed  among  the  heptad  elements.     Man- 
ganese forms  a  fluoride  MnF?,  and  is  probably  septiva- 
lent   in   the  permanganates;    as,   K2O,   Mn2O7    or  OK- 
Mnl03. 

NICKEL  AND  COBALT. 

498.  These  elements  are  strikingly  similar.    They  gen- 
erally occur   together   in    nature,  being  found  native  in 
meteoric  iron,  but  more  frequently  as  sulphides  or  arse- 
nides, associated  with  other  metals.     The  process  of  ex- 
tracting  the   nickel    and  cobalt  from  these  ores  is  very 
complicated.     From  the  oxides,  the  metals  are  obtained 
by  roasting  with    charcoal  at  white  heat;    or   from   the 
oxalates,   by  simple   ignition.     The   oxalic   acid   decom- 


252  CHEMISTRY. 

poses,  yielding  carbonic  oxide,  which  reduces  the  re- 
maining oxide.  Cobalt  is  the  less  abundant,  and  is  not 
produced  in  the  metallic  state  on  a  large  scale.  Nickel 
has  quite  an  extensive  use  in  certain  alloys,  as  German 
silver,  and  in  small  coins;  and  recently  has  been  em- 
ployed in  nickel-plating,  to  protect  steel  instruments 
from  rusting. 

499.  Both  metals  resemble  iron  in  their  physical  prop- 
erties.    They  are  white,  hard,  malleable,  and    tenacious 
metals,  the  tenacity  of  cobalt  even  exceeding  that  of  iron; 
and    are    also    strongly  magnetic,  but  less  so  than  iron. 
They  resist  oxidation  in  moist  air,  and    are    not   easily 
soluble  in  either  hydrochloric  or  sulphuric  acids.    Their 
best  solvent  is  nitric  acid. 

500.  Both  form  a  stable  series  of  salts,  in  which  they 
act    as   divalent   metals.     The    hydrated    salts    of  nickel 
are  generally  green,  but  yellow  when  anhydrous;  those 
of   cobalt    are    generally    rose-red    when    cold,    but    on 
heating,  blue,  becoming  anhydrous. 

501.  The  most  important  salt  of  nickel  is  the  sulphate, 
NiSO4  7H2O,    which    forms    crystals    isomorphous   with 
those  of  magnesium  sulphate.     It  also  forms  with  alka- 
line sulphates  double  salts;    as,  K2Ni(SO4)2GH2O. 

On  adding  caustic  soda  to  a  solution  of  the  sulphate,  an  apple- 
green  hydrate,  NiO,  H2O,  precipitates,  which  is  easily  soluble  in 
acids.  From  this  may  be  prepared  nickel  chloride,  NiCl2,  by  the 
addition  of  hydrochloric  acid.  On  adding  sodium  carbonate  or 
oxalic  acid  to  a  moderately  concentrated  solution  of  the  sulphate, 
bluish-green  precipitates  form,  which  are  respectively  carbonates 
or  oxalates  of  nickel. 

502.  The  most  important  salt  of  cobalt  is  the  nitrate, 
Co(NO3)2  +  6H2O,  a  deliquescent,  very  soluble,  rose-red 
salt.     Its   solution   treated   with    sodium    hydrate    yields 
CoO,  H2O,  which   is   at   first   blue   and  then  changes  to 


COBALT.  253 

rose-red.  Either  the  hydrate  or  the  nitrate,  when  heated, 
changes  to  the  brown  anhydrous  sesqui-oxide  Co2O3. 
This  is  an  important  agent  in  blowpipe  analysis.  It 
yields,  when  ignited  with  various  other  oxides,  residues 
of  characteristic  colors,  viz :  with  magnesia,  a  pink  mass ; 
with  zinc,  a  green  mass ;  and  with  alumina,  a  blue  mass. 
Still  more  remarkable  is  the  magnificent  blue  which  it 
communicates  to  borax  or  to  alkaline  silicates.  These 
reactions  have  also  been  used  in  the  arts  upon  a  large 
scale  to  produce  pigments  such  as  Hi n man's  green  (with 
ZnO)  and  Thenard's  blue  (with  A12O3),  for  imparting  a 
sapphire-blue  color  to  porcelain  glaze,  and  for  making 
blue  glass.  Smalt  is  blue  glass  ground  to  a  fine  powder 
and  washed. 

503.  Cobaltic  nitrite.     If  to  a  strong  solution  contain- 
ing   cobalt,    a    strong    solution    of   potassium    nitrite    is 
added,    and    then    enough    acetic    acid    to    liberate    the 
nitrous  acid,  all    the   cobalt,   upon   standing,  is   precipi- 
tated   as    a    difficultly    soluble    yellow    powder    (Co2O3, 
3K2O,  5N2O3).     Nickel    does   not  form  a  corresponding 
salt,  and  hence  this  difference  in  reaction  is  one  of  the 
means  used  to  separate  the  two  elements. 

504.  Cobaltous    chloride,    CoCl2.    is    obtained    in    red 
prisms  containing  6H2O,  by  dissolving  either  the  oxide 
or  the  carbonate  in  hydrochloric  acid.     If  a  drawing  is 
made   with    its    dilute   solution  upon  paper,  it  is  nearly 
colorless;    but,  when  heated   to    about  150°,  it  becomes 
anhydrous    and   appears   as   a  bright  blue,  which  again 
disappears  in  moist  air.     This   property   has    led    to    its 
use  in  a  so-called  chemical  hygrometer,  and  in   sympa- 
thetic inks. 

505.  Both,  nickel  and  cobalt,  when  their  dyad  solutions 
are  mixed  with  ammonia,  yield  a  hydrate  which  dissolves 
in  excess   of  ammonia.     The  solution  contains  a  double 


254  CHEMISTRY. 

salt  of  ammonia  and  the  salt  of  nickel  or  cobalt  used. 
If,  now,  chlorine  gas  be  passed  into  either  solution,  a 
black  precipitate  forms  which  is  the  hydrated  sesqui- 
oxide,  Ni.2O33H2O  or  Co2O33H2O.  The  same  precipi- 
tate forms  when  an  alkaline  hypochlorite  is  added  to 
cither  hydrate  in  the  presence  of  free  alkali.  In  these 
sesquioxides  both  metals  act  as  tetrads;  thus: 

O  Ni=0 

/     \  or    |  >0. 

0=Ni—    _:Ni=O        Ni=O 

Nickel  forms  no  other  tetravalent  compounds. 

506.  Cobalt  forms,  as  a  tetravalent  element,  several 
salts,  among  which  those  with  ammonia  and  cyanogen 
are  the  best  known. 

(1)  If  the  solution  of  cobaltous  hydrate  in  ammonia   is   exposed 
to  the  air,  it  gradually  absorbs  oxygen  to  form  cobaltic  compounds 
(of  Co2O3)  with  ammonia.     These  compounds   are   very  numerous 
and  of  complex  constitution.     They  may  be  very  generally  regarded 
as  ammonium  compounds,  in  which  the  double  atom  of  cobalt  has 
replaced  two  or  more  hydrogen  atoms  of  ammonium.     The  roseo- 
cobaltic  chloride  has  the  formula  Co2Clf,,  10H,N  -f  2H2O. 

(2)  If  to  a  solution  of  a  dyad  salt  of  nickel  or  of  cobalt,  potassium 
cyanide  in  solution  is  cautiously  added,  the  cyanides,  NiCy2  (green- 
ish) or  CoCy2  (brownish),  precipitate.     Both   dissolve  in  an  excess 
of  the  potassium    cyanide.     The   nickel    double    cyanide   suffers    no 
further   change.     Freshly   precipitated    mercuric   oxide   precipitates 
from  this  solution  nickel  oxide  completely.     If,  however,  the  cobalt- 
ous  double    cyanide    is   exposed   to  the  air,  it  forms  the  potassium 
cobalti-cyanide,  from  which  the  cobalt  is  not  precipitated  by  mer- 
curic oxide  nor   by  ordinary  reagents.     The  cobalt  in  this  is  prob- 
ably hexavalent,  thus: 

K2Cy3— Co<Cy3K 

ir  n     J.  IT     °r  K6>Co^2,4Cv3. 

K  Cy3>Co— Cy3K2 

This  difference  of  reactions  affords  the  most  accurate  method  of 
separating  nickel  from  cobalt. 


IRON  AND  MANGANESE.  255 

507,  It  remains  only  to  notice  a  very  curious  phe- 
nomenon. When  to  a  solution  of  calcium  hypochlorite 
a  few  drops  of  cobaltous  nitrate  are  added,  the  black 
sesquioxide  immediately  precipitates.  If,  now,  the  solu- 
tion is  heated  to  80°  C.,  oxygen  will  be  given  off  until 
all  the  hypocholorite  is  changed  to  calcium  chloride. 

A  very  small  quantity  of  the  Co2O3  is  capable  of  decomposing 
an  unlimited  quantity  of  the  hypochlorite,  CaO,  C12O  to  CaCl2  -(-  O2. 
The  alleged  reaction  is  that  the  hypochlorite  changes  the  Co2O3  to 
CoO3,  a  body  which  is  unstable  at  boiling  heat,  two  molecules  de- 
composing to  O3  and  Co2O3,  and  thus  becoming  capable  of  re- 
moving more  oxygen  from  the  hypochlorite. 

TESTS  FOR  NICKEL  AND  COBALT. — (1)  Their  dry  compounds, 
mixed  with  sodium  carbonate  and  heated  in  the  reducing  flame 
before  the  blowpipe,  yield  a  magnetic  powder. 

(2)  If  this   powder   yields    a   blue   borax   bead  in  the  oxidizing 
flame,    which    is    also    persistent   in    the   reducing   flame,    cobalt  is 
present. 

(3)  Cobalt   is   precipitated   by  potassium    nitrite,  while   nickel  is 
not. 

(4)  They  are  best   separated   by  their   reactions  with   cyanogen; 
but   this   process   is    too   dangerous   to    be    used    except   by  trained 
chemists.     The  cobalt  forms  a  cobalti-cyanide;  the  nickel  forms  no 
corresponding  salt. 


IRON  AND  MANGANESE. 

508,  These  metals  are  also  closely  related  in  most  of 
their  physical  and  chemical  properties,  and  are  fre- 
quently associated  together  in  nature.  They  act  as 
positive  elements  in  two  series  of  salts:  (1)  a  stable 
dyad  "ows"  series,  correspondent  in  formula  and  fre- 
quently isomorphous  with  those  of  the  magnesium  group, 
as  FeCl2,  MnSO4  ;  (2)  a  stable  tetrad  "zc"  series,  con- 
taining a  double  atom  in  which  they  are  quadrivalent, 
although  apparently  trivalent,  as  Cl3=Fe — Fe=Cl3  or 
Fe2Cl6.  The  sulphates  form,  with  alkaline  sulphates, 


256  CHEMISTRY. 

alums  which    arc    isomorphous  with    those    of  the    next 
group,  as  K20,  8O3  4-  *Y2O8HSO8  4.  24H20. 

They  act  also  as  negative  elements,  forming  salts  like 
K2MnO4,    which    are    isomorphous    with    chromates,    as 
K2CrO4.     They  form,  therefore,  a   connecting   link    be 
twee n  the  pairs  of  this  group. 

509.  Iron   is   found   native    in    meteorites,   which   arc 
sometimes  so  pure  that  they  can  be  wrought.     In  small 
quantities,  its   compounds   arc    found   every-where ;    and 
it    is    also    abundantly   found    in    numerous   and  thickly 
distributed    mines,    which    have    sometimes    almost    the 
dignity   of  mountains,   as    in    Michigan,  Wisconsin,  and 
Missouri. 

It  is  so  abundant  that  its  sulphides,  arsenides,  and 
other  ores  difficult  of  reduction  have  no  commercial 
value  as  sources  of  iron.  The  reducible  ores  are  its 
various  oxides  and  carbonates;  and  these  arc  worked 
only  when  found  in  considerable  quantities. 

510.  The  principal  of  these  useful  ores  are :  magnetite, 
Fe3O4   (Fe,  72  per  cent) ;    hematite,    with    its    varieties, 
clay   iron    stone,    specular  iron,  etc.,  Fe2O3   (Fc,  70  per 
cent);  spathic  iron.  Fe('o3  (Fe,  48  per  cent);  and  black 
band,  a  carbonate  associated  with  carbonaceous  matters. 
The  working  value  of  an  ore  frequently  depends  on  the 
mineral    deposits    with    which    it    is   associated,    as    coal 
and  lime.     One   of  the  best  ores  of  Ohio  is  a  carbonate 
containing  about  40  per  cent  of  iron. 

511.  These  oxy-compounds,  if  pure,  are  easily  reduced 
to   the    metallic    state    (wrought  iron)  by  smelting  with 
coal.     A    few   so-called   "  bloomery   forges"    are    now    in 
operation  in  the  United  States,  producing  wrought  iron 
directly  from  the  ore.     Generally  speaking,  the  mineral 
matters  with  which  the  ore  is  mixed  require  to  be  sep- 
arated,  and    the    smelting   process    becomes    more    com- 
plicated. 


IRON  MANUFACTURE. 


257 


The  Ordinary  Manufacture  of  Iron. 

512.  The  first  stage  consists  in  making  cast  iron.    This 
is   effected   in   tall   blast-furnaces,  whose   shape  will  be 
understood   from  the  fig- 
ure.    It  is,  however,  nec- 
essary   to    add    that    the 
pipes,  t,  at  the   base   are 
called     tuyeres,     through 
which  a  blast   of  cold  or 
of  hot  air  may  be  driven 
into  the  stack. 

We  need  to  consider  (1)  the 
nature  of  the  ore.  If  the  ores 
contain  carbonates,  they  are 
first  roasted  to  convert  them 
to  oxides.  This  process  also 
serves  to  expel  a  portion  of 
the  sulphur  with  which  they 
are  frequently  contaminated. 

(2)  The  nature  of  the  min- 
eral  matters,   or  gangue,  with 
which  the  ores  are   associated. 
It   is   indispensable   that   they 
should  be  converted  into  a  sort 
of  glass  or  fusible  slag.    Hence, 
if  the   ores  contain  clay,  they 

are  mixed  with  lime;  or,  if  they  contain  an  excess  of  lime,  they 
must  be  mixed  with  clay.  The  most  easily  fusible  slag  has  nearly 
the  formula,  6CaO,  Al2O3,9SiO2;  and  it  is  desirable  to  obtain  this 
compound  as  nearly  as  possible. 

(3)  Charcoal    yields   the   best   iron;    anthracite    coal,   almost   as 
good.     The  coal  should  be  free  from  sulphur,  and  should  not  cake 
in  the  furnace.     Caking  coals  require  to  be  changed  to  coke  before 
using.     Such   cokes   lose   a   portion  of  their   sulphur,   and   become 
almost,  if  not  quite,  as  serviceable  as  the  other  forms  of  carbon. 

We  have  now  the  crude  materials,  (a)  the  roasted  ores,  which 
are  oxides  of  iron;  (b]  the  lime  or  clay,  to  render  the  slags  fusible 
(they  are  called  fluxes);  (c)  some  form  of  carbon,  which  is  to  act 
both  as  a  fuel  and  as  a  reducing  agent;  and  (d)  a  blast  of  air  to 
furnish  oxygen  to  the  coal. 
Chem.-17. 


FIG.  92. 


258  CHEMISTRY. 

(4)  Now  suppose  the  furnace  has  been  properly  heated  to  avoid 
cracking  the  masonry,  and  a  layer  of  coal  is  burning  at  the  bottom. 
Then  a  suitable  mixture  of  roasted  ore  and  flux  is  added  from  the 
top  of  the  stack,  then  another  layer  of  coal,  then  another  layer 
of  ore  and  flux,  and  so  on  alternately  until  the  stack  is  nearly 
filled  up,  the  heat  being  maintained  by  the  air  blast  for  some 
hours. 

513.  The    chemical    processes    which    take    place    are 
these  : 

(1)  The  air  passing  through  the  tuyere  pipes  combines  with  the 
ignited  carbon  and  forms  carbonic  acid,  C -}- O2  =  C'O2.  (2)  This 
ascends  into  the  furnace,  and,  meeting  with  red-hot  carbon,  com- 
bines with  it  and  forms  carlx>nouR  oxide,  C -f  CO 2  =  2CO.  (3)  The 

carbonous  oxide,  acting  upon  the  iron  oxide,  reduces  it  to  the  me- 
tallic state,  Fe2O3  -+-  SCO  =  Fe2  -{-  ;}('(),.  (4)  At  the  same  time, 
the  heat  produced  renders  the  slag  fusible,  and  the  reduced  iron  is 
disseminated  through  it  until  it  can  gradually  sink  down  to  the 
hottest  part  of  the  furnace.  (">)  There  it  combines  with  a  small 
portion  of  the  carbon,  forming  cast  iron  (Fe4C?j,  a  fusible  com- 
pound which  settles  to  the  crucible  at  the  bottom  of  the  furnace. 
(6)  The  slag  accumulates  in  larger  quantities  than  the  cast  iron, 
and  is  drawn  off,  from  time  to  time,  through  apertures  provided 
for  that  purpose.  (7)  Finally,  when  the  cast  iron  has  accumulated 
in  sufficient  quantities,  it  is  run  through  channels  into  moulds  of 
sand;  and,  upon  cooling,  forms  rough,  cylindrical  masses,  which 
are  the  pig  iron,  or  cast  iron,  of  commerce. 

It  ought  also  to  be  noted  that  the  process  is  continuous.  As 
fast  as  the  slag  and  the  iron  are  drawn  off  at  the  bottom,  fresh 
materials  are  added  at  the  top,  and  the  process  goes  on  without 
stopping  for  years. 

514.  Cast  iron  has  many  varieties.     The  extremes  are 
white  and  gray  iron.    White  iron  is  a  hard,  brittle  com- 
pound   of  iron    and    carbon,  nearly  represented   by  the 
formula  Fe4C  (it  generally  contains  about  3  per  cent  C). 
It  is  not  suitable  for  castings,  because,  although  more  fusi- 
ble than  gray  iron,  it  is  less  liquid  when  fused,  and  fails  to 
fill  the  moulds  completely.    It  dissolves  completely  in  hy- 
drochloric acid,  yielding  hydrogen  associated  with  an  un- 
pleasant odor  of  some  hydro-carbon  compound.     On  the 


CAST  IRON. 


259 


other   hand,  when   gray  iron    dissolves    in    hydrochloric 
acid,  it  leaves  a  residue  of  graphitic  carbon. 

515.  Gray  iron,  therefore,  contains  most  of  its  carbon 
in  an  uncombined  state,  as  graphite.     It  is  so  soft  that 
it  may  be  easily  turned    in    a    lathe,   and    is   admirably 
fitted  for  castings.     An  intermediate  variety,  called  mot- 
tled cast  iron,  exceeds   both    the    other   varieties    in    te- 
nacity, and  is  used  for  cannon.     In  commerce  there  are 
eight  grades  distinguished. 

The  foundry  man  can  control  his  product  to  a  great 
extent,  although  he  may  obtain  pigs  of  different  grades 
at  the  same  casting.  Too  small  a  proportion  of  fuel — 
i.  e.j  too  low  a  heat — will  yield  white  iron. 

516.  Spiegel-eisen  is  a  crystalline  variety  of  white  cast 
iron,  containing  from  3  to    12    per   cent   of  manganese, 
and  a  large  amount  of  combined  carbon.    It  is  excessively 
hard  and  lustrous,  and  is  chiefly  used   in   the  Bessemer 
process  for  making  steel. 


FIG.  93. 


517.  Wrought,  or  bar,  iron  is  nearly  pure.  To  obtain 
it  from  cast  iron,  the  carbon  is  burned  away.  This  is 
effected  in  a  puddling  furnace  (Fig.  93),  which  is  a  re- 
verberatory  furnace  divided  into  two  parts. 


260  CHEMISTRY. 

In  one  side  the  fuel  is  placed,  and  the  flame  is  conducted  so  as 
to  play  on  the  hearth  of  the  other  side.  Upon  this  hearth  a  mix- 
ture of  iron  oxide  and  white  iron  is  placed.  It  soon  melts  and 
becomes  oxidized  upon  the  surface.  The  mass  is  now  thoroughly 
stirred  (puddled),  whereby  the  carbon  is  oxidized  and  escapes  as 
carbonic  oxide.  As  wrought  iron  is  less  fusible  than  cast  iron, 
the  mass  becomes  more  and  more  pasty,  until,  when  the  greater 
part  of  the  carbon  has  been  driven  oif,  it  assumes  a  pasty  condi- 
tion, or  "comes  to  nature,"  and  collects  in  a  spongy  mass  upon 
the  end  of  the  puddle.  It  is  then  taken  from  the  furnace  and 
beaten  or  squeezed  to  free  it  from  silicious  slags,  and  becomes 
welded  into  an  ingot,  or  bloom,  of  wrought  iron.  These  ingots 
are  reheated  and  rolled  into  bars,  to  give  the  metal  a  homogeneous 
and  fibrous  structure. 

It  is  to  this  fibrous  structure  that  the  tenacity  of 
wrought  iron  is  due.  Cast  iron,  when  broken,  shows  a 
granular  structure,  and  breaks  much  more  easily  than 
wrought  iron.  It  is  said  that  wrought  iron  loses  its 
fibrous  structure  and  becomes  granular  by  repeated 
concussions. 

518.  Wrought   iron   is   never    quite   pure.     The   best 
contains   a    minute    proportion    of  carbon    (from    0.1    to 
0.3  per  cent)  ;    but   this   can    hardly  be   considered  as  a 
disadvantage,  because  it  notably  increases  the  hardness 
and  tenacity  of  the  iron. 

Some  varieties  of  bar  iron  are  brittle  when  cold. 
This  defect  is  probably  due  to  the  presence  of  phos- 
phorus, and,  perhaps,  also  of  silicon.  This  is  called 
"  cold-shortness." 

The  presence  of  sulphur,  on  the  other  hand,  renders 
the  iron  brittle  when  hot.  This  defect  is  called  "  red- 
Bhortness."  Iron  containing  both  sulphur  and  phos- 
phorus has  both  defects,  and  is  difficult  to  weld  when 
hot,  and  is  brittle  when  cold. 

519.  Steel  is  a  product  intermediate  between  cast  and 
wrought  iron.     It  can  be  cast  like  pig  iron,  and  worked 
on  the  anvil  and  welded  like  wrought  iron.     Moreover, 


STEEL.  261 

it  possesses  th'e  invaluable  property  of  receiving  a  "  tem- 
per." Soft  steel,  if  suddenly  cooled  from  a  high  tem- 
perature, becomes  excessively  hard  and  brittle.  By 
subsequent  heating  it  may  be  rendered  as  soft  and 
tenacious  as  is  required.  This  process  is  called  "  draw- 
ing the  temper." 

520.  Steel  contains  from  0.5  to  1.5  per  cent  of  carbon. 
This  carbon  may  be  added  to  wrought  iron  by  heating 
it   for   several   days   at   about    1100°   C.,    or   below   the 
fusing   point  of  steel,    in    chests   packed   with    charcoal 
powder.     The   product   is   known  as  blistered  steel,  but 
it  is  far  from  being  uniform  in  its  composition.     When 
blistered  steel  is  melted  and  cast  into  ingots,  it  becomes 
homogeneous  in  structure  and  is  called  cast  steel. 

521.  The  Bessemer  process  converts  cast  iron  into  steel 
by  burning  away  a  portion  of  its  carbon. 

This  is  effected  by  running  several  tons  of  melted  cast  iron  into 
a  large  crucible,  or  converter,  provided  with  tuyeres  through  which 
a  strong  blast  of  air  can  be  blown.     Considerable 
heat  is  developed  by  this   operation;    nearly  all 
of  the  carbon  is  burned  away,  and  the  iron  be- 
comes nearly  bar  iron.     The  moment  when  this 
result  is  accomplished  may  be  determined  by  the 
spectroscope,  or  with  sufficient  accuracy  by  the 
practiced  eye   of  the   foreman.     Then  the  blast 
of  air    is    stopped,    and    a    quantity    of  melted 
spiegel-eisen,  sufficient  to  furnish  the   necessary 
carbon,  is  added,  and  the  mixture  is  allowed  to 
rest   for  a  few  minutes,  to   permit  all  gases  to  escape,  and  then  it 
is  cast  into  ingot  moulds. 

This  steel  is  of  inferior  quality  to  cast  steel,  but  is 
admirably  adapted  for  the  rails  used  in  railroads,  and 
for  other  purposes.  The  presence  of  -5-^-  of  its  weight 
of  phosphorus  renders  steel  brittle. 

522.  The    malleable    iron,    so-called,    which    is    daily 
growing  into  use,  is  simply  cast   iron   which   has   been 


262  CHEMISTRY. 

heated  for  days  in  boxes  packed  with  the  sesquioxide 
of  iron.  The  cast  iron  thereby  loses  enough  of  its 
carbon  to  become  assimilated  to  wrought  iron.  When 
the  process  is  well  conducted,  small  objects  of  brittle 
white  cast  iron,  as  buckles,  gate  hinges,  or  even  larger 
articles,  become  nearly  as  malleable  and  tenacious  as 
wrought  iron  ;  and  small  bars  so  treated  may  even  be 
drawn  into  the  finest  wire.  We  observe  that  this  is 
the  reverse  of  the  process  of  making  blistered  steel. 
(1)  In  steel,  the  carbon  is  added  by  heating  wrought 
iron  with  charcoal ;  (-)  in  malleable  iron,  the  carbon  is 
withdrawn  by  heating  cast  iron  with  ferric  oxide. 

523.  Pure  iron  is  readily  prepared  by  heating  its  oxide 
in  a  current  of  hydrogen  or  of  carbonous  oxide.     (£295). 

In  this  connection,  Exp.  30  is  very   interesting. 

Exp.  195.— The  apparatus  necessary  will  he  readily  understood 
from  the  figure.  (Use  apparatus  in  Fig.  27).  The  hydrogen  is  care- 
fully dried  by  sulphuric  acid,  and  allowed  to  escape  until  no  air 
remains  in  the  apparatus.  The  bulh  tube,  which  contains  a  small 
quantity  of  the  pulverized  oxide,  is  then  heated  to  redness  and 
becomes  reduced:  Fe2O3  -f  GH  —  2Fe  -f  3II2O;  or.  if  carbonous 
oxide  be  employed,  Fe2()3  -f  SCO  =  2Fe  f  Sri),.  The  reduced 
iron  must  be  allowed  to  cool  in  a  current  of  the  gas  before  the 
iron  is  poured  out. 

524.  Iron  so  reduced  is  a  black  powder.    It  so  readily 
oxidizes  that  it  may  be  set  on  fire  by  a  lighted  splinter; 
or,  if  poured  from  the  reduction  tube  while  warm,  takes 
fire    in    the   air   and    again   changes  to  the  oxide.     Pure 
iron    in    its    compact    form    is    a    silvery-white,  strongly 
magnetic    metal,    exceedingly  ductile,  malleable,  and  te- 
nacious, but   soft    enough  to  permit  its  being  easily  cut 
with  steel  files.     It  fuses  at  white  heat;  but,  fortunately 
for  the  arts,  before  reaching  this  temperature  it  becomes 
so  soft  that  it  may  be  wrought  on  the  anvil  and  welded. 
The  blacksmith  usually  sprinkles  sand  or  borax  on  the 
heated  metal,  in  order  to   form  with    the    oxide    film    a 


PROPERTIES  OF  IRON.  263 

fusible  slag,  which  may  be  forced  out  by  the  hammer, 
and  thus  leave  the  surfaces  clean.  They  then  cohere 
or  weld  without  difficulty. 

525.  Iron   does    not    oxidize    in    dry   air   at   ordinary 
temperatures.     (1)  When  heated  in  air,  a  blackish  "  scale 
oxide"  forms,  which    is   beaten  off  by  hammering.     (2) 
In  moist  air,  it  rapidly  oxidizes,  or  "rusts."     The  water 
decomposes,  and  ferrous  oxide  forms:    this   in   the  pres- 
ence   of  carbonic  anhydride  becomes  ferrous  carbonate ; 
and  this,  in  turn,  becomes  ferric  hydrate  (Fe2O3,3H2O). 
Unfortunately,  this  is  very  porous ;    and  these  changes, 
when    once    commenced,  go  on  with  increasing  rapidity 
until    the   entire    mass    is    corroded.      (3)    Heated    in   a 
current  of  steam,  iron  decomposes  water  readily ;   thus, 
3Fe  +  4H20  =  Fe3O4  +  8&. 

Dilute  hydrochloric  and  sulphuric  acid  dissolve  iron 
readily  with  evolution  of  hydrogen,  and  form  respect- 
ively ferrous  chloride  and  ferrous  sulphate.  Dilute 
nitric  acid  also  dissolves  it,  evolving  nitric  oxide  and 
forming,  when  the  action  is  rapid,  ferric  nitrate.  In 
strong  nitric  acid  (sp.  gr.  1.45)  the  iron  assumes  a 
"  passive  condition,"  in  which  it  is  neither  attacked  by 
the  strong  acid  nor  afterward  by  nitric  acid  of  ordinary 
strength  (sp.  gr.  1.35). 

526.  The  uses   of  iron   are  so  varied  and  well  known 
that   it   is   useless   to  attempt  to  enumerate  them.     The 
alloys    are    not   of  much    importance.     When    protected 
from  the  action  of  the  air  by  a  coating  of  tin,  it  forms 
the  tin  plate  of  commerce ;    and  when  coated  with  zinc, 
it  is  called  galvanized  iron. 

527.  The  compounds  of  iron.    Although  the  two  series 
of  iron    salts    differ   widely,   they   are    easily    converted 
from  one  form  to  the  other.     Solutions   of  ferrous   salts 
quickly  oxidize  in  the  air,  and  soon  manifest  the   pres- 
ence of  ferric  salts.    They  are  more  quickly  oxidized  by 


264  CHEMISTRY. 

nitric  acid  or  by  a  mixture  of  potassium  chlorate  and 
either  hydrochloric  or  nitric  acid.  On  the  other  hand, 
reducing  agents  like  nascent  hydrogen,  sulphuretted 
hydrogen,  stannous  chloride,  and  sulphurous  anhydride, 
convert  ferric  salts  to  ferrous. 

528.  Ferrous   salts,  when  crystallized,  have  generally 
a  green  color  and  astringent  taste.     Such  as  are  soluble 
can  be  easily  made  by  dissolving  iron  in  the  cold  dilute 
acid  required. 

Ferrous  sulphate,  FeSO4  -f  7H2O  (copperas  or  green 
vitriol),  may  be  obtained  pure  from  the  mixture  of  iron 
sulphide  and  sulphuric  acid  used  in  making  sulphuretted 
hydrogen  :  FeS  +  H2SO4  =  11^  +  FcSO4.  The  remain- 
ing solution  requires  merely  to  be  filtered  and  crystal- 
lized out,  preferably  under  a  layer  of  alcohol.  Exposed 
to  the  air,  the  crystals  absorb  oxygen  and  form  a  basic 
ferric  sulphate.  Hence,  ferrous  sulphate  may  act  as  a 
reducing  agent,  as  already  noted  in  gold.  It  is  largely 
used  as  a  disinfectant,  and  for  making  "white  indigo." 

Ordinary  black  ink  is  made  from  a  solution  of  nut-galls  and  a 
sulphate  of  iron.  If  ferric  sulphate  is  used,  the  ink  is  black  when 
first  applied;  if  ferrous  sulphate  is  used,  the  ink  is  first  a  pale  green, 
but  becomes  black  on  exposure  to  the  air. 

Ferric  sulphate,  Fe2($O4)3,  is  a  yellowish,  difficultly 
soluble  body,  obtained  by  oxidizing  the  ferrous  sulphate. 
The  basic  sulphate  is  used  in  making  Nordhausen  acid. 

529.  On  heating  iron  wire  in  a  stream  of  dry  chlorine 
gas,  a  volatile  anhydrous  chloride  is  formed,  which  col- 
lects  in    the    cooler   parts   of  the    tube.     (1)  When   the 
iron   is    heated    to  redness,  white   or  yellowish   shining 
scales   of  ferrous    chloride    form ;    (2)   at   a    lower   heat, 
and  especially  in  the  presence  of  air,  iridescent  spangles 
of  ferric  chloride  form. 

Hydrated  ferrous  chloride  is  formed  when  iron  wire 
is  dissolved  in  hydrochloric  acid,  and  the  mixture  left 


COMPOUNDS  OF  IRON.  265 

to  cool  in  closed  vessels.  This  is  changed  to  ferric 
chloride  by  the  addition  of  nitric  acid  until  the  solution 
becomes  a  yellowish  brown.  It  forms,  when  dried,  a 
yellow,  deliquescent  mass.  It  is  also  to  be  noted  that 
both  chlorides  volatilize  even  from  their  solutions  when 
heated. 

530.  Ferrous   carbonate,    FeCO3,    is   probably   formed 
when  sodium  carbonate  is  added  to  a  solution  of  ferrous 
sulphate;    but  it  soon  loses  its  carbonic  anhydride,  oxi- 
dizes, and  yields  ferric  oxide.     It  is  soluble  in  an  excess 
of  carbonic  anhydride,  and  is  found  dissolved  in  mineral 
waters.     It  also  exists  in  most  blue  clays.     When  these 
mineral  waters  are  exposed  to  the  air,  the  ferric  hydrate 
precipitates,  sometimes  forming  an  iridescent,  oily  looking 
film  on  the  water;    and,  when   such    clays   are   burned, 
they  impart  a  red  color  to  the  bricks,  tiles,  etc. 

531.  Iron  exhibits  strong  affinities  for  sulphur.    Ferric 
sulphide,    FeS2,    occurs    abundantly    in    nature   as   iron 
pyrites,    in    yellow,    hard    crystals    strongly   resembling 
gold  (fool's  gold),  but   easily    distinguished   from    it   by 
its    lower    density    and    superior    hardness,   and    by   its 
giving   off  sulphurous   anhydride  when  strongly  heated 
in  air.     This  last  reaction  renders  it  an  available  means 
for  the  preparation  of  sulphuric  acid. 

When  a  mixture  of  iron  filings  and  sulphur  (||  Fe, 
|J  S)  are  heated  together,  they  combine  and  form  a 
grayish-black  mass  of  ferrous  sulphide,  FeS,  which  is 
invaluable  for  the  preparation  of  sulphuretted  hydrogen. 
There  are  many  other  sulphides,  corresponding  to  the 
various  oxides. 

532.  The  consideration  of  the  oxides  of  iron  has  been 
reserved  to  this  point,  because  in  them  we  have  valua- 
ble tests  of  iron. 

(1)  A  solution  of  a  ferrous  salt,  when  mixed  with  a 
solution  of  sodium  hydrate,  yields  a  white  precipitate 


266  CHEMISTRY. 

of  ferrous  hydrate,  Fe(OH)2,  which  readily  oxidizes  in 
the  air — becoming  green,  then  black,  and  finally  reddish 
brown. 

(2)  The    reddish   brown   result  is  ferric  hydrate,  Fe2 
(OH)6.     It  is  obtained  directly  as  a  voluminous  precip- 
itate by  adding  sodium  hydrate  to  a  solution  of  a  ferric 
salt.     After  ignition,  it  shrinks  in  volume  and  is  changed 
to  Fe2()3.     Ammonia    produces   the  same  precipitate  in 
ferric  salts;    but   forms  with    ferrous   compounds   soluble 
double  salts. 

(3)  When    iron    is    burned    in    air,  a   black  compound 
forms  which   is  principally   Fe3O4,  "  scale  oxide."     This 
form    occurs    also    in    nature,  and   some   specimens  of  it 
arc  natural   magnets. 

(4)  When    iron    and   saltpeter  are  fused  together,  and 
then  treated   with   water,  a    purple    solution   is  obtained, 
which  is  supposed  to  contain   K2^>  FC^SJ  potassium  fer- 
rate.    Ferric  anhydride,   FeO3,  has  never  been  isolated. 

Special  Tests  for  Iron. 

(1)  When  sulphuretted  hydrogen  is  passed  through  acid  solutions 
of  ferric  salts,  they  are  reduced,  with  separation  of  sulphur,  hut  no 
further  change  is  produced. 

(2)  Alkaline  sulphides  precipitate  both    ferric   and    ferrous    salts 
as  ferrous  sulphide,  FeS,  a  black  pulverulent  precipitate. 

(3)  Ammonium  sulphocyanide,  (NII4)CyS,  changes  solutions  of 
ferric    salts    to    a    beautiful   blood-red  color,  even  when  the  iron  is 
present  in  very  small  quantities. 

(4)  Distinctive   reactions   are   produced  when  solutions  of  ferro- 
and  ferri-cyanide  of  potassium  are  added  to  solutions  of  iron,  very 
slightly  acidulated. 


Ferrocyanide,  ( 
K4(FeCy61     { 

Ferricyanide,    ( 
K8(FeCye)     { 

WITH  FKRROUS  SALTS. 

Everitt's  White, 
K2Fe"(FeCy6) 

Turnbull's   Blue, 
Fe"3(FeCy6)2 

WITH  FERRTC  SALTS. 

Prussian  Blue, 

(Fe"-2)2(FeCy6)3. 

No  precipitate;  solu- 
tion becomes  brown. 

MANGANESE.  267 


MANGANESE. 

533.  Manganese   is   related   not   only  to  zinc,  to  iron, 
and   to    chromium,    but    probably    also    to    chlorine.     It 
generally  occurs   in    nature  as  an  oxide,  MnO2,  Mn2O3, 
or  as  "  wad"  which    is   a   mixture  of  these  with  earthy 
matters. 

The  metal  is  seldom  prepared,  but  may  be  obtained 
from  its  oxide  by  reducing  with  carbon  at  white  heat. 
It  is  very  hard  and  brittle,  slightly  magnetic,  easily 
oxidized  in  moist  air,  and  capable  of  decomposing  hot 
water. 

534.  It  forms    four   series   of  compounds.     (1)   As   a 
dyad  element,  salts  like  MnCl2  or  MnSO4,  obtained  by 
heating  its  oxides  with   hydrochloric  or  sulphuric  acid; 
as,  MnO2  -f  4HC1  =  2H2O  +  MnCl2  +  C12   or  MnO2  + 
H2SO4  =  MnSO4  -f  H2O  -f  O.     These  salts  are  pinkish 
colored,  and   crystallize  in  forms  isomorphous  writh  zinc 
salts,    as    MnSO4  -f-  7H2O.      They   are    the.  usual    com- 
pounds in  which  manganese  acts  as  a  positive  element. 
Their  solutions,  when  treated  with  sodium  hydrate,  yield 
a  white  precipitate  of  hydrated  mangarious  oxide,  which 
rapidly  oxidizes  in  the  air,  and   finally  becomes   brown 
Mn2O3,  311 2O.     When  ammonium  sulphide  is  added   to 
solutions    of  these    salts,   it  forms   flesh-red    manganous 
sulphide,  MnS,  a  characteristic  test,  not  only  by  reason 
of  its  color,  but  also  because  it  is  the  only  sulphide  of 
the  group  which  is  soluble  in  acetic  acid. 

(2)  As  a  tetrad  element,  in  oxides  like  MnO2  (pyro- 
lusite],  or  with  a  double  atom  like  Mn2O3  (Braunite). 
These,  when  heated  with  hydrochloric  acid,  yield  free 
chlorine  and  form  manganous  chloride. 

There  is,  besides,  an  unstable  green  sulphate  of  this 
group,  which  forms  a  moderately  stable  alum  with  alka- 
line sulphates,  as  K2O,  SO3  -f  Mn2O3,3SO3  +  24H2O. 


268  CHEMISTRY. 

(3)  As   a   hexad    element,   neither   MnO3   nor  MnCl6 
are  known ;  but,  when  any  oxide  of  manganese  is  fused 
with  saltpeter,  a  deep-green,  easily  soluble  mass  is  ob- 
tained,  which   is   potassium   manganate,   K2O,  MnO3  or 
K2MnO4.     This   body   is   so    unstable    that   it   is  easily 
decomposed  by  water  or  by  acetic  acid,  forming  a  rose- 
red  solution  of  the  permanganate. 

(4)  The    potassium    permanganate    has    the    formula 
K2O,  Mn2O7  or  KMnO4.     As  this   salt   is    isomorphous 
with    the   potassium   perchlorate   KC1O4,  it  is  supposed 
that  manganese  acts  in   this   as   a   septad   element   like 
chlorine. 

535.  Potassium  permanganate  crystallizes  in  beautiful 
red  rhombic  prisms,  freely  soluble  in  water.     It  is  more 
stable  than  the  manganate,  but  both  are  strong  oxidizing 
agents,  readily  giving  up  most  of  their  oxygen  and  re- 
verting to  manganous  oxides,  especially  in  the  presence 
of  free   acids.     Hence,   the   potassium    permanganate  is 
much  used  in  volumetric  analysis. 

Exp.  196. — Acidulate  a  solution  of  a  ferrous  salt,  and  add 
drop  by  drop,  a  solution  of  a  permanganate.  The  red  color  of  the 
permanganate  solution  does  not  remain  permanent  until  all  the 
ferrous  salt  has  been  oxidized  to  ferric: 

10FeSO4  -f  2KMnO4  -f  8H2SO4  = 

5Fe2(S04),  +  K2SO4  -f  2MnSO4  -f  8H2O. 

Hence,  if  the  quantity  of  the   permanganate   used   is   known,  that 
of  the  ferrous  oxide  present  can  be  calculated. 

From  the  readiness  with  which  both  the  manganate 
and  permanganate  salts  are  decomposed,  they  are  used 
as  disinfecting  agents.  They  are  especially  useful  in 
detecting  the  presence  of  decomposing  organic  bodies 
in  waters  used  for  drinking. 

536.  The  uses   of  manganese   are   chiefly   (1)   in   the 
preparation    of   the    disinfecting    agents    already    men- 
tioned;   (2)   in    making   glass,  to  which   it   imparts   an 


CHROMIUM  AND  ALUMINIUM.  269 

amethyst  color  when  alone,  or,  when  mixed  in  the 
required  amount,  destroys  the  green  color  produced  by 
iron ;  (3)  in  the  preparation  of  chlorine  used  in  the 
manufacture  of  bleaching*  powder. 

TESTS. — Some  of  the  tests  for  manganese  have  already  been  in- 
dicated. The  most  characteristic  are  the  flesh-red  sulphide  and  the 
potassium  manganate  formed  by  fusion  with  niter. 

In  its  other  reactions  it  agrees  generally  with  the  members  of 
this  group,  except  that  its  white  hydrate  in  alkaline  solutions  is 
more  readily  oxidized  by  air  or  by  chlorine  to  the  brown  sesqui- 
oxide,  Mn2O3. 

CHROMIUM  AND  ALUMINIUM. 

537.  These  elements  are  closely  related  to  iron.     Chro- 
mium   is   considered   first,  because   it   forms  a  series  of 
dyad   compounds   represented  by  CrCl2  and  the  double 
sulphate,  K2O,  CrO,  (SO3)2  -f  6H2O.     These   chromous 
compounds  are  generally  unstable ;    and  chromous  chlo- 
ride is  so  readily  changed  to  its  higher  compounds  that 
it  is  one  of  the  most  powerful  reducing  agents  known. 
They  are  also  seldom  met  with,  and  will   not   be   con- 
sidered further.     It   also   forms   an   unimportant   oxide, 
Cr3O4,  resembling  magnetite. 

538.  In  the  tetrad  series,  both  of  these  elements,  A12O3 
and  Cr2O3,   form    salts  which    strongly   resemble   ferric 
salts,  and  are  isomorphous  with  them.     The  only  oxide 
of  aluminium  is  A12O3,  which  acts  both  as  a  weak  base 
and  as  a  weak  acid. 

Chromium  forms  also  a  hexad  series,  like  iron  and 
manganese.  In  tnis  series  it  acts  as  a  negative  ele- 
ment, as  K2O,  CrO 3 

539.  The  most  important  ore  of  chromium  is  chrome 
iron,  FeCr2O4,  or,  perhaps,  FeO,  Cr2O3.     It  also  occurs 
in  a  few  other  minerals   as  red   lead  ore,  PbCrO4,  and 
is  the  green  coloring  principle  of  the  emerald. 


270  CHEMISTRY. 

Metallic  chromium  has  no  use  in  the  arts,  and  is 
seldom  prepared.  It  is  one  of  the  most  infusible  of 
metals,  and  so  hard  as  to  scratch  glass.  Combined 
with  steel,  it  forms  an  exceedingly  hard  alloy,  which 
has  found  employment  in  cutting  glass,  sharpening 
knives,  and  in  making  drills. 

540.  The  compounds  of  chromium.     Unlike  the  metals 
previously  studied,  chromium    ores  are  worked  only  for 
the  sake  of  their  salts.     The  first  formed  are  the  chro- 
mates;  the  oilier  salts  are  derived  from  them  by  subse- 
quent treatment. 

The  pulverized  chrome  iron  ore  is  mixed  with  potassium  car- 
bonate and  potassium  nitrate,  and  is  then  heated  in  a  current  of 
air  on  the  hearth  of  a  reverberatory  furnace.  The  Cr2O3  is  oxi- 
dized to  2OO3,  and  unites  with  the  potassium  to  form  potassium 
chromate. 

541.  Potassium    chromate,    K2O,  CrO3.     This    salt    is 
obtained    by  lixiviating   the  ignited  mixture  and  evapo- 
rating   the    solution.      It    forms    very    soluble,    yellow, 
rhombic  crystals. 

542.  Potassium   bichromate,  K2O,  2(YO3  or  K2O2O7, 
is  the  usual  salt  found  in  commerce.     It  is  prepared  by 
mixing    the    solution    of  the  chromate  with   nitric  acid: 
2(K20,  Cr03)  +  II20,  X205  =  H2O  +  K2O,  X2O5  +  K2O, 
2CrO3.     The    salt    is    soluble   in    10   parts  of  water,  and 
crystallizes   in    beautiful    red,   tabular  prisms.     With  an 
excess  of  nitric  acid,  a  red  ter-chromate  is  also  formed, 
K2O,  3CrO3. 

543.  Chromic  anhydride,  CrO3.  is  obtained  by  mixing 
a    saturated    solution    of  the   bi-chromate   with   a    little 
more  than  its  own  bulk   of  sulphuric  acid.     When  this 
mixture   cools,    the   chromic  anhydride  separates  out  in 
crimson   needles.     These   crystals    are    deliquescent,  and 
are  very  soluble  in  water.    Although  a  moderately  stable 


CHROMIUM  COMPOUNDS.  271 

body,  it  is  a  powerful  oxidizing  agent,  and  is  instantly 
reduced  by  organic  matters  and  by  all  reducing  agents, 
as  H2S,  SO2,  Zn,  and  even  by  HC1.  Hence,  its  solution 
can  not  be  filtered  through  paper,  and  the  crystals 
formed  as  above  described  must  be  separated  from  the 
mother  liquor  by  decantation,  and  dried  upon  a  porous 
tile. 

Exp.  197. — Place  upon  a  saucer  dry  chromic  anhydride,  and 
pour  upon  this  a  little  alcohol.  The  CrO3  is  reduced  partly  to 
O2O3  and  partly  to  CrO2;  the  alcohol  is  changed  to  aldehyde: 
3(C2H6O)  alcohol  +  2CrO3  =  3H2O  +  Cr2O3  +  3(C2H4O)  aldehyde. 
So  much  heat  is  evolved  that  the  alcohol  is  frequently  set  on  fire. 

544.  Chromic  acid,  H2O,  CrO3  or  H2CrO4,  has   never 
been  isolated;  but  there  is  a  large  number  of  chromates 
which  are  generally  yellow  or  red  salts.     Many  of  these 
are  used  as  pigments,  and  are  easily  obtained  by  mixing 
a  solution  of  potassium  bi-chromate  with  a  solution  of  a 
salt 'of  some  other  metal. 

(1)  With  lead  acetate,  PbCrO4  forms  as  a  beautiful  yellow  pre- 
cipitate, which  is  "chrome  yellow."     "Chrome  green"  is  a  mixture 
of  this  with  Prussian  blue. 

(2)  With  barium  chloride  it  forms  a  pale  yellow  precipitate  of 
13aCrO4,  which  is  "  yellow  ultramarine." 

(3)  With  silver  nitrate  and  with  mercurous  nitrate,  the  products 
are  red  chromates,  which  are  beautiful  colors,  but  too  expensive  to 
be  used  as  pigments. 

There  are  numerous  other  chromates,  most  of  which, 
except  those  of  the  alkalies  and  of  strontium,  calcium, 
and  magnesium,  are  insoluble  in  water.  They  are  all 
decomposed  by  heat,  with  evolution  of  oxygen. 

545.  Lead  chromate  is  used  as  an  oxidizing  agent  in 
organic    analysis.     When    heated    with    sulphuric    acid, 
the  chromates  are  reduced  with  evolution  of  oxygen  — 
e.  g.,  2CrO3  +  3H2SO4  =  Cr2O33SO3  +  3H2O-[-3O;  and 
by  hydrochloric  acid,  with  evolution  of  chlorine : 

2Cr03  +  12HC1  =='  Cr2Cl6  +  6H2O  +  6&1. 


272  CHEMISTRY. 

These  last  reactions  will  take  place  when  a  chromate  is  heated 
with  these  acids,  and  an  excess  of  acid  must  be  used  in  order  to 
combine  with  the  base  of  the  chromate. 

546.  There   are   also  several  compounds  of  this  scries, 
of  great  theoretical  interest.     One    of  these  is  (YO2C12, 
in  which  two  chlorine  atoms  have    displaced    one    atom 
of  oxygen.     It    is   obtained   by   distilling  a   mixture   of 
common    salt    and    sulphuric    acid    with    potassium    bi- 
chromate,   as    a    blood-red    liquid,   which    is    a    powerful 
oxidizing    agent,    commonly    called    chlorochromic    anhy- 
dride.    At    the    same    time,  there  forms   a   salt  which  is 
K2Cr2O6Cl2,  or   a    potassium  bi-chromate  in  which  one 
atom  of  oxygen  is  replaced  by  two  atoms  of  chlorine. 

547.  Chromium    acts    as   a   negative    element   in   this 
series.     It   also   acts   as   a    positive   element    in  a  totally 
different  series.      Chromic  oj'i<h>.  Cr2O3,  is   obtainable   as 
an  amorphous  green  powder  by  igniting  chromic  anhy- 
dride, or  by  igniting  any  chromate  containing  a  volatile 
base,  as  NH4  or   Ilg.     It    is    used    as   a   green    pigment, 
and  is  especially  valuable  for  imparting  a  beautiful  green 
color  to  glass  and  porcelain.     This   oxide    is   almost   in- 
soluble in  acids. 

548.  The  other  compounds  of  this  series  are  most  easily 
prepared    from    chrome    alum.      Chrome    alum    is    itself 
made  (1)  by  heating  a  mixture  of  potassium  bichromate 
and  sulphuric  acid  with  alcohol ;  or  (2),  better,  by  pass- 
ing  through   the   mixture,  in  the  cold,  a  stream  of  sul- 
phurous anhydride :  thus,  K2O.2CrO3-f-H2SO4-f  3SO2  = 
H2O-f(K2O,SO3-fCr2O3,3SO3).    On  crystallizing,  splen- 
did dark  purple  octahedra  form,  which  contain  24H2O, 
or  are  KCr(SO4)2  -f  12H2O. 

549.  Chromic  hydrate,  Cr2O3,3H2O,  may  be  precipi- 
tated  from    a   solution  of  chrome  alum  by  any  alkaline 
hydrate.     It  is   a  bulky,   greenish-blue   powder,  soluble 
in   excess   of  soda   or   potash,  but  is  again  precipitated 


CHROMIUM  COMPOUNDS.  273 

on  boiling.  It  is  a  feeble  base,  but  is  remarkable  for 
forming  with  the  acids  two  classes  of  salts,  which  are 
identical  in  formulae,  but  differ  in  some  of  their  prop- 
erties. (1)  Violet  salts  formed  (when  a  rise  in  tempera- 
ture is  avoided)  by  dissolving  the  hydrate  in  acids. 
These  salts  are  crystallizable,  and  are  insoluble  in  alco- 
hol. (2)  Green  salts,  which  are  obtained  on  boiling 
the  violet  salts.  They  are  uncrystallizable,  but  are  sol- 
uble in  alcohol.  The  green  salts,  when  kept  in  solution 
for  months,  gradually  recover  their  violet  color  and 
become  crystallizable.  These  are  marked  examples  of 
isomerism  among  inorganic  compounds. 

550.  Chromic    sulphate,    Cr2(SO4)3  +  18H2O,    is    ob- 
tained by  dissolving  chromic  hydrate  in  dilute  sulphuric 
acid.    If  prepared  in  the  cold,  it  has  a  violet  color ;  but, 
when  heated,  becomes  green,  reverting  after  a  time  in 
solution  to  the  violet  modification. 

551.  Chromic   chloride,   O2C16  -f  12H2O,  forms  when 
chromic    hydrate,  or   any  chromate,  is  dissolved  in  hy- 
drochloric acid.     An  anhydrous  chloride   of  a   beautiful 
peach-blossom  color,  which  is  scarcely  soluble  in  boiling 
water  or  in  acids,  is  formed  when  chlorine  gas  is  passed 
over  ignited  chromic  oxide. 

It  is  also  supposed  that  there  is  a  perchromic  acid, 
H2O,  Cr2O7,  which  is  formed  when  peroxide  of  hydro- 
gen is  added  to  chromic  salts.  A  blue  solution  is 
thereby  formed,  which  is  a  delicate  test  for  chromium  ; 
but  neither  the  acid  nor  its  salts  have  been  obtained. 

552.  Uses   of  chromium.     The  chromates  are  valuable 
oxidizing  agents,  especially  in  the  presence  of  sulphuric 
acid.     Potassium  bichromate  solution  is  frequently  used 
in    galvanic    batteries.     Principally,  however,  chromium 
compounds   are   used  in   dyes  and  pigments.     They  are 
generally  yellow  or  green.     The  green  printing  ink  used 
in  "  green-backs  "  owes  its  color  to  chromium. 

Chem.— 18. 


274  CHEMISTRY. 

TESTS  FOR  CHROMIUM. — (1)  All  chromium  compounds,  when 
heated  with  borax,  yield  an  emerald-colored  bead  which  is  very 
characteristic. 

(2)  All  chromium  compounds,  when    fused  with  soda  and  niter, 
yield  a  yellow  chromate  soluble  in  water. 

(3)  These  chronmtes,  neutralized  with   acetic   acid,  yield    charac- 
teristic precipitates:    yellow  with  lead  and  barium;  red  with  silver 
and  mercurous  salts. 

(4)  The  eliminates  in  solution  are  reduced  to  salts  of  the  sesqui- 
oxide  by  sulphuretted  hydrogen.     These  reduced  solutions,  or  solu- 
tions  of  salts   of  the  sesqui-oxide,  yield,  with  ammonium  sulphide 
or    ammonia,    greenish    or    bluish    hydrates,    somewhat    soluble    in 
excess  of  the  precipitant,  but  again  precipitated  upon  boiling. 

ALUMINIUM. 

553.  Aluminium    is    one    of   the    most    abundant    and 
most  widely  distributed    of   the    elements.      It  never  oc- 
curs   native,    and    seldom    occurs    as    an    oxide    (emery, 
corundum),  but  more  frequently  as  a   fluoride  (cryolite). 
It  forms,   however,  an  almost   endless  variety  of  double 
silicates,    which     constitute    the    great    majority    of    the 
rocks  of  the  earth,  as  granite,  basalt,  slates,  shales,  and 
clays.     The  feldspars  and   micas  are  silicates  of  alumina 
combined    with    silicates    of  potash,  or  soda,  or  lime,  or 
magnesia,    or    a    mixture    of  these   with    small    amounts 
of  other  bases.     When    such    minerals    as    these    disinte- 
grate  by  the    action    of  atmospheric   agencies,  ordinary 
clays,    potter's    clay,    fire    clay,   and    kaolin    are    formed, 
which  are  aluminic  silicates,  more  or  less  contaminated 
with  other   substances.     Alumina    is    also    a    constituent 
of  several  precious  stones,  as  the  sapphire,  ruby,  topaz, 
emerald,  and  garnet. 

554.  Aluminium  is  best  prepared  by  fusing  the  double 
chloride  of  aluminium  and  sodium  with  metallic  sodium: 
2NaAlCl4  +  GNa  =  8NaCl  +  2A1.     The  addition  of  cryo- 
lite (Al2Na6F12)  facilitates  the  reduction.    Jt  is  a  bluish- 
white   metal,  of  very  low  specific  gravity  (2.5G),  which 


ALUMINIUM.  275 

is  quite  malleable,  ductile,  and  tenacious.  It  is  also 
remarkably  sonorous,  which  property  it  also  communi- 
cates to  many  of  its  alloys.  Aluminium  is  not  oxidized 
in  the  air  nor  affected  by  sulphuretted  hydrogen.  It  is 
not  attacked  by  cold  dilute  sulphuric  and  nitric  acids, 
but  dissolves  readily  in  hydrochloric  acid  and  in  solu- 
tions of  caustic  soda  and  potassa. 

Its  many  valuable  properties  render  it  desirable  that  it  should 
be  more  abundantly  used  in  the  arts  and  in  the  various  appliances 
of  the  household;  but  the  cost  of  its  preparation  (which  is  depend- 
ent on  the  price  of  sodium)  has  restricted  its  application  mainly  to 
the  construction  of  delicate  balances,  small  weights,  and  other  in- 
struments in  which  lightness  is  desired  and  only  a  moderate  strength 
needed. 

Much  has  been  hoped  for  the  alloys  of  aluminium. 
Aluminium  bronze  contains  9  parts  of  copper  and  1 
part  of  aluminium.  It  is  very  strong,  difficultly  fusible, 
unaltered  in  air,  but  has  not  found  a  wide  application 
in  the  arts. 

555.  The  compounds  of  aluminium.  As  already  stated, 
aluminium  forms  but  one  series  of  compounds,  the  tet- 
rad, represented  by  A12O3  and  by  A12C16. 

Alum  is  the  most  important  salt.  The  simplest  process 
by  which  it  is  manufactured  consists  (1)  in  forming 
aluminium  sulphate  by  heating  a  pure  clay  or  shale 
with  sulphuric  acid.  On  lixiviating  this  mass,  an  alu- 
minium sulphate  is  obtained:  A12O3,  3SO3  -}-  18II2O. 
(2)  Because  this  salt  is  difficultly  crystallizable,  it  is 
converted  into  a  double  salt  containing  either  K2O,S03 
or  (NH4)2O,  SO3,  which  crystallizes  in  beautiful  octa- 
hedra,  in  a  condition  which  insures  the  purity  of  the 
commercial  article.  This  is  effected  simply  by  mixing 
the  solution  of  aluminium  sulphate  with  the  requisite 
amount  either  of  potassium  or  of  ammonium  sulphate, 
and  allowing  the  solution  to  crystallize.  The  crystals 
have  the  formula  K2O,  A12O3,  4SO3  +  24H2O  and 


276  CHEMISTRY. 

(KE4)2O,  A12O3,4SO3  -h24H2O;    or,  written   in    mole- 
cular formula4, 

KA1(S04)2  +  12II20  and  XII4A1(SO4)2  -f  12H2O. 

Formerly,  potassium  alum  was  the  most  common;  but 
now  the  ammonium  alum  has  become  the  usual  com- 
mercial article,  because  the  ammonium  sulphate  is  ob- 
tained at  a  low  price  from  the  refuse  liquors  of  gas 
works.  The  value  of  either  alum  depends  only  on  the 
amount  of  aluminium  sulphate  it  contains.*  Of  late 
years,  aluminium  sulphate  has  found  its  way  into  com- 
merce under  the  name  of  concentrated  alum. 

556.  Aluminium  hydrate,  A1(OII\V  is  formed  as  a 
white  gelatinous  precipitate  when  ammonia  or  (avoiding 
excess)  any  other  alkali  or  alkaline  carbonate  is  added 
to  a  solution  of  alum.  With  a  small  amount  of  alkaline 
carbonate,  a  basic  sulphate,  A12O3.  S()8,  is  formed.  The 
use  of  alum  in  the  arts  depends  upon  the  fact  that  both 
the  hydrate  and  the  basic  salt  have  the  power  of  com- 
bining with  the  coloring  principles  of  organic  dyes, 
like  cochineal,  to  form  insoluble  pigments  called  lakes, 
as  carmine. 

In  applying  this  reaction  to  calico  printing,  (1)  the  stuffs  are 
dipped  in  ti  solution  containing  this  basic  alum,  when  the  cloth 
becomes  impregnated  with  the  aluminium  compound.  (2)  By  the 
action' of  air  or  of  steam,  the  aluminium  becomes  firmly  incorpo- 
rated with  the  fibers  of  the  cloth.  This  is  the  "ageing  process." 
(3)  The  cloth  is  now  dipped  into  the  dye-vat,  and  the  aluminium 
combines  with  the  coloring  matters  and  fixes  them  within  the  fiber. 
Such  colors  are  likely  to  be  "  fast,''  that  is,  durable;  and  the 
alumina  is  said  to  act  as  a  ''mordant,"  because  it  bites  or  holds 
the  colors. 

*  The  word  alum,  which  was  once  used  specifically  to  denote  potash  alum,  is 
now  generioally  applied  to  all  double  sulphates  which  crystallize  in  octahedra 
with  24H2O,  and  contain  a  monad  sulphate  together  with  a  tetrad  sulphate; 
thus,  R'2O,  SO3  +  R^2O3, 3SO3  +  24H2O.  In  this  way  we  may  have  a  large  series 
of  iron,  chromium,  and  aluminium  alums  with  either  of  the  alkalies,  potassium: 
sodium,  etc.  There  are  also  a  number  of  pseudo-alums  with  22H2O,  containing 
dyad  metals  like  magnesium. 


ALUMINIUM  COMPOUNDS.  277 

Aluminium  hydrate  is  easily  soluble  in  dilute  acids, 
forming  salts  such  as  A1(NO3)3  ;  A12C16.  The  chloride 
forms  a  number  of  double  salts  with  the  alkaline  chlo- 
rides. 

557.  Aluminium   oxide,    A12O3,   or   alumina,  occurs   in 
nature    nearly    pure    in    corundum,    and    in    an    impure 
state  as  emery.     Both  of  these  are  extremely  hard,  and 
are    used    for   polishing.     It  is  artificially  obtained  as  a 
white  amorphous  powder  by  igniting  aluminium  hydrate 
or  ammonia  alum.     It  is  then  an  almost  infusible  mass, 
and    is    insoluble    in    acids.     It    is    rendered    soluble  by 
fusion  with  carbonates  of  soda  or  of  potash.     The  com- 
pounds thus  formed  are  aluminiates,  in  which  the   alu- 
minium acts  as  a  negative  element. 

558.  Potassium  aluminiate,  K2O,  A12O3  or  KA102,  is 
crystallizable;    sodium   aluminate   is   a    white    amorphous 
solid.     Solutions  of  either  of  these   are   decomposed  by 
acids,   even    by   carbonic,    forming    aluminium    hydrate. 
Hence,  they  may  be  used  as  substitutes  for  alum. 

The  affinities  of  aluminium  in  both  these  classes  of  salts  are  very 
feeble;  for,  if  a  solution  of  an  aluminium  salt  is  mixed  in  atomic 
proportions  with  one  of  an  aluminiate,  both  are  decomposed  with 
the  formation  of  aluminium  hydrate;  for  example: 

A12C16  -f  6KA102  +  12H20  =  4A12O3,  3H2O  +  6KC1. 

559.  Ultramarine,  a   beautiful   blue   pigment,  was  for- 
merly obtained   from    lapis    lazuli,    one    of  the   precious 
minerals.    After  careful  analyses  of  the  mineral,  attempts 
were  made  to  reproduce  the  pigment  artifically,  by  fusing 
together  the  materials  in  the  proportions  so  ascertained. 
Finally,  it  Avas  found  that  by  fusing  together  pure  clay, 
sodium   sulphate,    and    charcoal,  a  green  "  ultramarine " 
was  produced  which  is  a  valuable  pigment.    This  product, 
mixed  with  sulphur  and  again  fused,  yields  a  blue  ultra- 
marine  which    fairly    rivals    in   brilliancy   of   color  the 
native  mineral,  and  is  much  cheaper. 


278  CHEMISTRY. 

This  may  be  considered  as  one  of  the  triumphs  of  chemistry; 
although,  even  now,  the  cause  of  the  beautiful  blue  color  in  either 
the  native  or  artificial  ultramarine  has  not  been  satisfactorily  as- 
certained. We  know  only  that  they  contain  sodium-aluminium 
silicates  and  sodium  polysulphide  as  their  principal  ingredients. 

560.  Aluminium  silicates  are  of  great  importance.  They 
are  seldom  found  pure  in  nature,  being  generally  con- 
taminated with  iron  and  other  bases.  The  purest  is 
kaolin,  a  white  friable  clay  derived  from  the  decompo- 
sition of  feldspars.  These  clays  are  used  in  the  manu- 
facture of  porcelain;  the  more  impure  clays,  in  the 
manufacture  of  bricks. 

Limestones  containing  about  20  per  cent  of  aluminium 
silicate  when  calcined  yield  hydraulic  cements,  which 
have  the  property  of  hardening  under  water. 

TESTS.  —  (1)  Solutions  of  aluminium  salts  are  precipitated  as 
white  gelatinous  hydrates,  A1(OH)3,  by  ammonium  hydrate  and 
ammonium  sulphide,  almost  completely. 

("2)  The  hydrate,  when  moistened  with  cobalt  nitrate,  and  ignited, 
forms  an  infusible  blue  mass. 

Gallium,  discovered  bv  Lecoq  de  Boisbaudran  in 
1870,  is  probably  related  to  aluminium.  It  has  l>oen 
obtained  in  whitish  octahedral  crystals  (sp.  gr.  5.9), 
which,  though  harder  than  iron,  melt  at  a  temperature 
of  about  :>0°(1.  Its  atomic  weight  has  recently  been 
determined  09. 9. 

Recapitulation. 

The  elements  in  this  group  form  compounds  in  which  they  enter 
as  dyads,  tetrads,  and  hexads. 

The  dyad  compounds  strongly  resemble  those  of  Mg,  Zn,  and  Cd, 
being  isomorphous  with  them,  and  capable  of  replacing  them 
in  the  double  salts  with  the  alkalies,  as  in  W2O,  SO3  -f  Rr/O, 
SO  3  -j-  6H2O.  All  these  dyad  compounds  are  precipitated  by 


RECAPITULA  TION.  279 

sodium  hydrate,  avoiding  excess,  as  white  or  greenish  hydrates, 
soluble  in  a  large  excess  of  ammonium  chloride.  H2S  does 
not  precipitate  Mg;  it  precipitates  CdS  in  acid  and  alkaline 
solutions,  and  the  others  only  in  alkaline  solutions  or  by  alka- 
line sulphides,  as  sulphides.  Their  protoxides  are  generally 
strong  bases. 

The  hydrates  of  the  tetrad  series  are  weak  bases  of  the  formula 
K/r2O3,  3H2O.  They  are  precipitated  on  adding  to  their  neu- 
tral solutions  almost  any  dyad  carbonate.  The  best  reagent  is 
BaCO3.  They  do  not  dissolve  in  ammonium  chloride,  and 
hence  are  also  precipitated  by  NH4HO.  These  hydrates  also 
in  some  cases  act  as  weak  acids.  Their  sulphates  form  with 
alkaline  sulphates  double  salts  containing  24H2O  (alums).  Cr 
and  Al  do  not  form  sulphides  in  the  wet  way. 

Some  of  these  elements  form  also  a  hexad  series,  in  which  they 
act  as  negative  elements.  The  best  representatives  of  this  class 
of  compounds  are  the  salts  of  the  acids  of  manganese  and 
chromium,  as  K2MnO4,  K2CrO4. 

These  three  series  differ  widely  from  each  other.  Al  forms  only 
tetrad  compounds.  The  dyad  compounds  of  the  others  are 
changed  by  oxidizing  agents  to  tetrad  compounds;  some  (not 
all)  of  the  tetrads  may  be  further  oxidized  by  fusion  with  niter 
to  hexad  compounds.  On  the  other  hand,  reducing  agents  will 
convert  hexads  to  tetrads,  and  most  tetrads  to  dyads.  These 
elements  therefore  exhibit  a  very  flexible  character. 

It  is  not  improbable  that  Mn  and  Cr  also  act  as  heptads  In 
KMnO4  and  in  perchromic  acid. 

The  metals  of  this  group  have  important  uses  in  the  arts;  iron 
being,  perhaps,  the  most  used  and  the  most  useful  metal  known. 
Many  of  their  alloys  and  salts  find  important  applications  in 
the  arts.  Fe,  Co,  Ni,  and  Mn  are  magnetic  elements. 

It  may  also  be  noted  that  while  these  elements  agree  in  some  par- 
ticulars, they  differ  in  many  others.  Some  form  by  preference 
dyad  compounds;  Al  only  tetrad;  Cr  is  best  known  as  a  hexad. 
Nevertheless,  the  pairs  which  make  up  the  sub-groups  are 
strongly  related. 


CHAPTER    XVI. 

KERAMICS    AND    GLASS. 

561.  Bricks  are  made  from  clay.  This  is  kneaded 
with  a  small  amount  of  water,  so  as  to  render  the  mass 
homogeneous;  then  moulded  into  shape;  then  thoroughly 
dried  in  the  open  air;  and,  finally,  burned. 

Not  all  varieties  of  clay  are  suitable  for  this  purpose.  All  clays 
shrink  on  drying;  but  the  very  plastic  clays,  which  are  composed 
for  the  greater  part  of  aluminium  silicate,  shrink  so  much  that  they 
crack  and  fall  into  pieces.  Hence,  an  admixture  of  sand  is  neces- 
sary, which  must  be  supplied,  if  not  naturally  present  in  the  clay, 
in  order  to  give  the  right  consistence  to  the  mass.  In  tropical 
countries,  the  bricks  are  not  burned,  but  are  only  sun-dried.  These 
are  at  best  very  friable,  and  are  suitable  only  for  low  structures. 

A  small  quantity  of  lime  or  of  feldspar  is  also  a  useful  constit- 
uent of  the  clay;  for,  when  the  bricks  are  burned,  these  substances 
fuse  and  serve  to  cement  the  particles  of  the  rl.-iv  together.  An 
excess  of  lime  renders  the  bricks  too  brittle. 

"When  the  clays  contain  no  ferrous  carbonate,  the  bricks,  when 
burned,  have  a  yellow  color.  The  red  color  of  ordinary  bricks  is 
due  to  the  conversion  of  the  ferrous  carbonate  to  the  ferric  oxide, 
by  the  action  of  the  heat  and  the  atmospheric  oxygen. 

Pire-bricks  are  made  from  clays  which  contain  neither 
lime  nor  iron.  These  clays  fuse  less  easily  than  the 
impure  varieties,  but  they  are  also  capable  of  resisting 
the  action  of  fire,  and  are  therefore  employed  for  the 
lining  of  furnaces  and  for  crucibles. 

All    bricks    are    porous,    excepting   the    few   that    are 
burned   in    immediate  contact  with  the  fire.     These  be- 
come so  over-heated  that  their  materials  fuse  and  form, 
a  sort  of  glaze  over  their  surface. 
(280) 


POTTERY  AND  PORCELAIN.  281 

The  so-called  terra-cotta  wares  are  made  in  the  same 
manner,  except  that  a  greater  care  is  taken  in  moulding 
the  clay  and  in  burning. 

562.  Ordinary  pottery  is  made   from  the  better  quali- 
ties of  clay  mixed  with  sand.     Drain  pipes  and  tiles  are 
fashioned  by  machinery.     Most  of  the  hollow  vessels  are 
fashioned  by  hand  upon  a  potter's  wheel.     The  articles 
are  then  allowed  to  dry  very  slowly.    When  thoroughly 
dry,  they  are  baked  in  kilns.     Porous  goods,  like  drain 
pipes    and    flower  '  pots,    receive    no    further   treatment. 
Stoneware   vessels   are  glazed  in  a  very  simple  manner 
by  a  process  known  as  salt  glazing. 

The  ware  is  coated  with  a  thin  film  of  sand  by  dipping  into  a 
mixture  of  fine  sand  and  water.  It  is  then  intensely  heated  in  the 
kiln,  and  a  quantity  of  damp  salt  thrown  in.  The  joint  action  of 
the  steam  and  the  salt  converts  the  sand  into  sodium  silicate,  which 
fuses  to  a  glass  on  the  surface  of  the  ware. 

Other  of  the  cheaper  forms  of  pottery  are  glazed  by  dipping  the 
wares  into  a  mixture  of  clay  and  litharge.  This  fuses  in  the  kiln 
to  a  lead  glass. 

563.  Porcelain.     In  the  manufacture  of  porcelain,  es- 
pecial care  is  taken  in  selecting  a  nearly  pure  aluminium 
silicate :  this  is  kaolin.     But  it   is   too    infusible    a  sub- 
stance   to   be    used    alone,    and,    therefore,    requires   the 
addition    of   some    more    fusible    material,    as    feldspar. 
The  Vienna  porcelain  and  "  china  "  contain  quartz  also. 

The  materials  are  first  ground  together,  mixed  with  water,  and 
moulded  like  ordinary  pottery  into  any  required  shape,  and  then 
are  allowed  to  dry  slowly  in  the  air.  These  dried  vessels  are  then 
burned  in  kilns,  in  which  a  high  temperature  may  be  obtained, 
and  are  thereby  baked  to  a  white,  porous  body,  which  is  incorrectly 
termed  biscuit  ware.  It  then  requires  to  be  glazed.  The  best 
glazing  is  obtained  by  dipping  the  biscuit  ware  in  water  containing 
a  mixture  which  very  nearly  resembles  the  original  materials,  only 
a  little  more  fusible,  and  sometimes  containing  chalk  or  gypsum. 
The  ware  is  again  reheated  to  a  temperature  sufficiently  high  to 
fuse  the  glaze,  and  is  then  ready  for  market. 


282  CHEMISTRY. 

There  are  several  varieties  of  porcelain :  (1)  a  very 
hard  sort,  like  that  of  China  and  Japan,  which  contains 
a  notable  amount  of  quartz;  (2)  a  softer  sort,  like  that 
of  Sevres,  which  is  quite  translucent.  This  translucency 
is  secured  by  the  admixture  of  ^fritt"  (which  consists 
of  a  vitrified  mixture  of  sand  and  alkaline  materials)  to 
the  kaolin.  (3)  The  English  porcelain,  which  is  quite 
hard  but  opaque,  contains  a  large  proportion  of  calcined 
bones. 

In  the  less  valuable  varieties  of  porcelain,  the  glaze  frequently 
contains  lead  or  boracic  acid  mixed  with  the  silicates.  This  glaring 
requires  a  less  temperature  for  fusing  in  the  second  baking;  but  it 
is  liable  to  crack,  because  it  is  not  homogeneous  in  structure  with 
the  body. 

564.  Glass  requires  that  the  materials  of  which  it  is 
composed  should  be  capable  of  being  thoroughly  fused 
together,  and,  on  cooling,  yield  an  amorphous,  trans- 
parent mass,  not  easily  affected  by  water  or  by  atmos- 
pheric agencies.  It  is  a  mixture  of  various  silicates, 
of  which  the  most  common  are  those  of  lime,  sodium, 
and  potassium. 

The  cheapest  variety  of  glass  (boitlc  glasx]  is  a  double  silicate 
of  alumina  and  lime.  This  mixture  is  so  difficultly  fusible  that 
sodium  silicate  is  generally  added.  The  other  varieties  of  glass 
either  contain  no  alumina  or  a  very  small  quantity. 

Ordinary  window  glass  is  a  mixture  which  may  be 
very  nearly  represented  by  the  formula,  Na2Ca4SiO3. 

The    materials    used    in    its    preparation    are    clean    white    sand, 
slaked  lime,  and  sodium  carbonate;    or,  instead  of  the  last,  a  mix- 
ture of  sodium  sulphate  with  sufficient  charcoal    to  decompose  the    v 
sulphuric  acid.     All  sodium  glasses  have  a  bluish  tinge,  from  which 
potassium  glass  is  free. 

The  best  plate  glass  is  also  chiefly  a  silicate  of  soda 
and  lime,  but  also  contains  potassium  silicate. 

Crown  glass  and  Bohemian  glass  contain  no  soda.    They 


GLASS.  283 

have  approximately  the  formula,  K4Ca315SiO3.  They 
are  beautiful,  clear  glasses,  well  adapted  for  optical 
purposes.  * 

Flint  glass  is  a  double  silicate  of  potassium  and  lead 
prepared  by  fusing  together  the  purest  white  sand  or 
flint,  calcined  and  ground,  with  lead  oxide  and  refined 
pearl  ash.  Other  materials  are  also  added  in  small 
quantities,  to  prevent  the  reduction  of  the  lead  (KNO3), 
or  to  remove  the  color  which  would  be  produced  by  the 
presence  of  iron  (As2O3  or  MnO2).  Its  approximate 
formula  is  K4Pb310SiO3.  The  presence  of  the  lead 
silicate  greatly  increases  the  fusibility  of  the  glass,  and 
also  adds  to  its  luster  and  beauty.  It  is  much  used  for 
ornamental  purposes,  as  fine  cut  glass,  f  In  optical  in- 
struments, lenses  of  flint  and  crown  glass  are  frequently 
combined  to  form  achromatic  lenses.  The  dispersive 
powers  are  made  to  neutralize  each  other,  and  yet  leave 
a  considerable  index  of  refraction. 

Other  silicates  are  frequently  used  in  glass,  as  baryta 
and  zinc.  Sometimes,  also,  a  quantity  of  boracic  acid  is 
used  to  replace  a  portion  of  the  silica.  . 

565.  Many  metallic  oxides  impart  characteristic  colors 
to  glass.  Ferrous  silicate  produces  a  green  glass;  ferric 
silicate,  a  yellow  which  is  hardly  noticeable  when  in 
small  quantities.  Hence,  -except  for  green  bottle  glass, 
it  is  desirable  to  oxidize  the  iron  which  is  scarcely  ever 
absent  from  the  sand.  This  is  eifected  by  niter,  arse- 
nious  oxide,  or  red  lead.  Manganese  binoxide  also  de- 
colorizes green  ferrous  silicate;  but  it  is  a  disputed 
question  whether  it  effects  the  change  by  acting  as  an 
oxidizing  agent,  or  by  producing  a  glass  of  a  comple- 
mentary color,  since  by  itself  it  yields  an  amethyst 
purple  glass. 

The  agents  used  to  impart  colors  to  glass  are  princi- 

*  Index  of  refraction,  1.53;  coefficient  of  dispersion,  0.02. 
t  Index  of  refraction,  1.64 ;  coefficient  of  dispersion,  0.04. 


284  CHEMISTRY. 

pally  these:  red,  Cu2O;  ruby,  purple  of  Cassius  (Au); 
amethyst,  MnO2  ;  blue,  CoO  ;  green,  FeO,  Cr2O3,  CuO  ; 
yellow,  Sb2O3  ;  greenish  yellow,  U2O3.  An  excess  of 
lead  oxide  also  produces  a  yellow  glass. 

566.  The  manufacture  of  glass  can  only  be  sketched. 

The  materials  are  fused  together  in  large  pots  made  of  fire-clay, 
and  are  then  permitted  to  remain  for  some  time  to  allow  air-bub- 
bles to  escape,  and  to  remove  the  glass  scum  which  rises  to  the 
surface.  It  is  then  taken  from  the  pots  and  wrought  into  the 
shape  required.  Much  of  our  glass-ware  is  blown,  as  bottles. 
Tumblers,  glass  plates,  etc.,  are  generally  moulded. 

All  glass-ware,  after  being  shaped,  requires  to  be  carefully  an- 
nealed. This  is  effected  by  a  process  of  slow  cooling.  The  hot 
ware  is  passed  through  a  long  chamber  so  arranged  that  the  heat 
is  gradually  diminished,  and  the  glass  is  taken  from  the  extreme 
end  quite  cool.  Unannealed  glass  is  very  liable  to  crack  with 
sudden  changes  of  temperature. 

Cut  gla.sfi  receives  additional  treatment,  being  ground  and  after- 
ward polished  on  emery  wheels. 

Recapitulation. 

Bricks,  ordinary  pottery,  and  porcelain  require  that  the  materials 
used  (clay,  kaolin)  should  be  difficultly  fusible. 

These  materials  are  kneaded  together,  dried,  and  baked.  Stone- 
ware and  porcelain  are  then  covered  with  a  glaze,  and  baked 
a  second  time. 

Grlass  requires  that  the  materials  used  should  be  easily  fusible,  and 
furnish  a  transparent  mass. 

Glass  requires  no  second  baking,  but  requires  a  careful  annealing 


ORGANIC   CHEMISTRY. 


CHAPTER  XVII. 

COM-POUNDS    OF    CARBON. 

567.  The  compounds  of  carbon  are  so  numerous  and  so 
intimately  related  to  each  other  that  it  is  convenient  to 
study  them  after  the  general  principles  of  Chemistry 
have  been  mastered.  The  laws  which  govern  in  their 
formation  and  transformations  are  in  no  respect  different 
from  those  of  the  other  elements.  This  division  of  the 
science  is  frequently  termed  Organic  Chemistry,  because 
many  of  the  carbon  compounds  have  been  obtained  from 
plants  and  animals.  Such,  for  example,  are  starch,  cane 
sugar,  albumin,  and  glue.  Other  "organic"  compounds 
have  been  obtained  from  these  by  the  natural  processes 
of  decay  and  fermentation,  as  the  grape-sugar,  alcohol, 
and  acetic  acid  that  are  so  derived  from  starch. 

568.  In  1828,  Woehler  obtained  urea  from  ammonium 
isocyanate.  Now,  as  the  cyanogen  compounds  may  be 
obtained  from  potassium  cyanide,  KCN,  and  this  by  di- 
rect union  of  its  three  elements,  Woehler's  discovery  is 
that  urea  and  its  derivatives  are  obtainable  by  synthesis. 
Since  that  date,  hundreds  of  organic  compounds  have 
been  produced  wholly  or  partly  by  synthesis.  By  aid 
of  the  electric  spark,  carbon  and  hydrogen  unite  directly 
to  acetylene,  C2H2.  Acetylene  in  presence  of  nascent 
hydrogen  becomes  ethylene,  C2H4  ;  this  by  incorporation 
of  a  molecule  of  water  is  converted  to  ethyl  alcohol, 

(285) 


286  ORGANIC  CHEMISTRY. 

C2H5OH,  and  from  this  a  host  of  other  compounds  usu- 
ally reckoned  as  starch  derivatives. 

Moreover,  acetylene  3(C2II2),  when  strongly  heated, 
is  condensed  to  benzene,  CGII6.  This  is  the  starting- 
point  from  which  the  aromatic  compounds  arc  derived. 
These  are  so  numerous  as  to  require  special  treatises, 
and  include  such  well  known  substances  as  benzole  and 
salicylic  acids,  aniline,  and  indigo. 

569.  The  compounds  which    have   been   obtained    from 
plants  contain:    (1)  Only  carbon  and   hydrogen;   as,  tur- 
pentine, (\  0H1(;.    Or  (2)  more  frequently,  carbon,  hydro- 
gen, and  oxygen  ;  as,  cellular  tissue  and  starch,  C6H10O6; 
grape -sugar,     C6II12Ori:    and    the    fats;    as,    tri-stearin 
C3H5(C18H85O2)3.     Or   (I))   they   are    nitrogenous   sub- 
stances  like  glue  and  albumin,  nearly  represented  by  the 
formula,   ^72^1, 18\1 8O22S.      But    (4)    intimately   mixed 
with     these    are    complex    substances    containing    small 
quantities  of  phosphorus;  as,  lecithin.     These  four  classes 
of  bodies    contain    but   six    elements;    but   besides  these, 
others  are  found  in  the  ashes  both  of  plants  and  animals, 
such  as  Ca.  Na,  K,  ('1,  F. 

570.  Any  element  may  become  associated  with  carbon 
in  compounds  which  any  chemist  would  class  as  organic: 
as  chloroform,  CIIC13,  zinc  ethyl  (C2II.)2Zn.     These  ar- 
tificial compounds  are   daily   increasing   in    number,  and 
are  often  of  great  theoretical  interest,  inasmuchTas  they 
are   important    factors   in    promoting    chemical    changes, 
and   often   indicate,  with    greater   or   less   clearness,   the 
structure  of  complex  molecules. 

571.  The  simplest  saturated  compounds  of  tetravalent 
carbon  are   mars'h  gas,  CH4  ;   carbonic  anhydride,  CO2  ; 
carbonic  disulphide,  C\S2 ;   and  prussic  acid,  HCN.     Any 
one  of  these   may  be  regarded   as  a  source  from  which 
numerous  compounds  are  derived.     It  is  often    possible 
to  arrange  these  compounds  in  series  which   exhibit  a 


COMPOUNDS  OF  CARBON. 


287 


regular  increase  in  vapor  density,  in  boiling  and  melting 
points,  etc.  Those  that  are  near  each  other  in  the  series 
are  always  very  much  alike,  but,  of  course,  the  differ- 
ences increase  with  wider  separation,  and  the  remote 
members  of  a  series  are  physically  quite  unlike. 


GENE 
FORM 


P  r 

B    1 

§  $ 


W 


55  rtf 
12    H 


*-  :     «    a  a 


p   o   p  p   o    o 

a  a  "a  a 


33       O 

w  3 

3     3 


>•     W 

E      g. 


p    p' 

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288  ORGANIC  CHEMISTRY. 

572.  Any  saturated  hydrocarbon  may  be  the  starting- 
point  from  which   other  compounds  are  derived  by  the 
substitution  of  other  radicals  in  place  of  one  or  more  hy- 
drogen atoms.     Thus  from  ethane,  C0II6,  or  its  hydride, 
C2II5II,   its  haloid  derivative,  as  C2115C1,  its   hydroxide, 
C2H5OH,  its  oxide  (C2H5)2O,  etc.     A  selection  of  such 
derivatives  constitutes  a  heterologous  series. 

573.  Each  homologous  series  is  supposed  to  increase  by 
substituting  the  univalcnt  radical   methyl,  CH3,  for  one 
of  the   II   atoms   in   the   preceding  term.     The  effect  of 
this  is  to  increase  the  term   by  CII2,  as  if  the  divalent 
radical  methane  had   been  inserted    between  two  carbon 
atoms.     This  fact  will  be  rendered  clear  by  a  few  graphic 

formula'. 

H 

Methane,  CH4  is  II     C     II.     The  first  substitution  of  CH3  for  H 
H 

II  II 
gives  ethane,  C2H6,  or  II     ('    C     H,  which  might  also  be  written 

II  H 

C2H5H,    and   called   ethyl    hydride,   or   as  CH3-CH3,   and   called 
di-methyl. 

H   H   II 
The  next  substitution  gives  C3H8,  propane,  H    C    C    C    H,  or 

ii  ii  ii 

CH3-  CH2    CH3,  or  C3H7  H,  propyl  hydride,  and  also  CH3-  C2H5, 
methyl-ethyl. 

H   H   H    H 
Butane  isC4H10  =  H    C-  C-  C    C    H  =  CH3    CH2    CH2    CH3> 

H    H   H    H 

or  it  is  butyl  hydride,  C4H9H,  or  methyl  propyl,  C3H7     CH3,  or 
di-ethyl,  C2H5    C2H5. 

Dissected  formulas  like  these  are  of  great  service,  and 
the  student  should  accustom  himself  to  consider  that 
the  radicals  which  are  represented  in  them  are  actual 
entities  as  much  so  as  an  atom  of  chlorine  or  of  sodium. 


COMPOUNDS  OF  CARBON. 


Z89 


574.  Whenever  two  carbon  atoms   unite,  at  least  two 
"bonds"  must  become  satisfied.     The  maximum  combin- 
ing   power  of  n,  carbon    atoms,  is   CuH2n-j-2,  which  is 
that   of  the   paraffin   series.     Such    unions   must   always 
go  by  pairs,  and  the  number  of  hydrogen  atoms  in  any 
saturated  hydrocarbon  must  be  an  even  number. 

In  the  olefine  series,  CnH2n,  the  first  two  carbon  atoms  must  be 
doubly  joined,  as  ethylene,  C2H4,  or  CHa  — CH2J  propene,  C3H6, 
or  CH2  =  CH  •  CH3 ;  butene,  C4H8,  or  CH2  =  CH  •  CH2  •  CH3,  and 
the  succeeding  terms  by  an  increase  of  CH2,  as  previously  de- 
scribed. The  acetylene  series,  CnII2n_2,  has  two  carbon  atoms  trebly 
joined;  as, 

acetylene,  H    C  =  C    H,  or  CH  =  CH,  and  allylene,  HC  =  C  •  CH3. 

It  will  be  noted  that  methyl,  CII3,  ends  most  of  these  formulae. 
It  is  supposed  to  be  peculiarly  susceptible  of  chemical  change. 
The  radical  at  the  other  end,  CH3,  or  CH2  =  CH,  or  CH  =  C., 
may  be  regarded  as  the  nucleus  about  which  the  complete  molecule 
is  gathered. 

575.  The   aromatic   hydrocarbons  start  from  benzene, 
which    is    thought  to    contain   six    CH   groups   of  equal 
chemical  activity.     This  idea  finds  expression  in  various 
glyptic  formula)  which  represent  the  carbon  atoms  united 
in  "closed  chains,"  (=CH)6,  as: 

C-H 


HC 


HC 


CH 


H-C 


H-C 


C-H 


C-H 


Any  hydrogen  atom  in  these  may  be  replaced  by  CH3, 
or  by  any  other  monovalent  radical.  In  this  way  one 
or  several  "open"  chains  may  be  added  to  the  benzene 
nucleus;  as,  C6H5,  CH 2 OH  =  benzene  alcohol, 

or  C6H4,  (COOH)2,  phthalic  acid. 
These  compounds  will  be  considered  in  Chapter  XXVI. 

Chem.— 19. 


290  ORGANIC  CHEMISTRY. 

The  conception  of  open  and  closed  chains,  and  a  modification 
known  as  a  "cleft"  chain,  is  often  serviceable  in  tracing  chemical 
changes  in  complex  compounds;  but  the  student  must  remember 
that  glyptic  formula?,  and  even  rational  formula1,  are  attempts  to 
represent  to  the  eye  the  facts  ascertained  in  chemistry.  They  are 
useful,  because  they  enable  the  student  to  group  together  a  large 
number  of  facts,  and  to  frame  theories  which  afford  a  satisfactory 
explanation  of  many  such  groups;  but  it  can  not  be  claimed  for 
them  that  they  are  in  any  sense  a  picture  of  the  molecular  structure 
of  any  compound  whatever. 

576.  Any  member  of  any  series  of  saturated  compounds 
may   be   taken    as    the   .source    from    which    radicals   are 
derived    by    removal    of  one    or    more    hydrogen    atoms. 
The    paraffin    series    may  be  made  to  yield    the  radicals 
shown   in   the  table  on   p.  2!U. 

577.  Bodies  are  classed  as  saturated  if  they  can  exist 
in  the  free  state,  and  if  they  form  compounds  with  chlo- 
rine, etc.,   only  by  substitution,  or,  in   a   narrower  sense, 
if  all   their  theoretical   "bonds"  are  satisfied.     They  arc 
classed  as  radicals  if  they  can   not  exist  in  the  free  state, 
but   form    stable    compounds    by    combining   with    them- 
selves;  as,  CII3-CH3,  dimethyl;   and    if  the}'  form   com- 
pounds   with    chlorine,   etc.,   by    <nhlition.      We    know  of 
compounds  obtained   from  ethylene,  C0II4   (which  exists 
in    the    free    state)    of   the    formula',    C2II3C'l;    C2II2C12, 
which   are   ''substitution"    products,   and    also   an    "addi- 
tion"   product,    (12II4(M2.     Hence,    hydrocarbons,   which 
contain  an  even  number  of  hydrogen  atoms,  such  as  the 
olefines,  may  act  as  saturated  molecules  or  as  artiad  radi- 
cals.    In  the   latter  case   they  are   said   to  "open"  their 
bonds, 

CH2  .  CH2  +  Cl2  =  CH2Cl-CH2ri, 

which    is   the   same    as  saying    that   they    revert   to  the 
preceding  series. 

578.  Every  hydrocarbon   must   be  a   radical   if  it  con- 
tains an   odd   number  of  hydrogen  atoms.     The  olefiues 


COMPOUNDS  OF  CARBON. 


291 


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292  ORGANIC  CHEMISTRY. 

and  acetylenes  furnish  perisad  radicals  similar  in  formulae 
to  those  of  the  paraffins;  but  of  course  different  in  prop- 
erties; thus,  C3II5  represents  the  trivalent  propenyl,  the 
third  derivative  from  propane,  C3H8,  and  also  the  uni- 
valent  allyl,  the  first  derivative  from  propene,  C3II6. 

579.  Most  organic  compounds,  whose  molecular  struct- 
ure   is   known,   may   be   considered    to   be   derived    from 
the  hydrocarbons.     Such  organic  compounds,  when  once 
formed,  are  units,  and  may  give  rise  to  other  series  of 
radicals.     Any  saturated  compound  whatever  may  be  di- 
vided in  theory  (that  is,  on  paper)  into  any  two  parts. 
Each  of  these  will  be  a  radical,  and  each  have  the  same 
valency.     None  of  these  radicals  are  of  use,  except  those 
which  express  some  fart  observable  in  the  formation  of  a 
compound   or  in   its  subsequent  reactions.*     Acetic  acid 
is  a  good  illustration.     Its  percentage  composition  is  very 
well  expressed  by  the  empirical  formula,  CII2O,  but  its 
vapor  density  (30)  requires  a  molecular  formula  double 
that,  or  C2H4O2.     Its  first  rational  formula,  II-C2H3O2, 
expresses  the  fact  that  one  of  its  hydrogen  atoms  is  re- 
placeable by  the  metals,  as  in  silver  acetate  AgC2H3O2  ; 
the  second,   C2II3O-OII,   that   the   haloid   elements  may 
displace  hydroxyl,  as  in  acetyl  chloride,  C2H3O-C1;  the 
third,  CII3CO2H,  that  it  may  be  obtained   from  marsh 
gas,  CII8II,  and  furnish  it;  the  fourth,  that  the  carbonyl 
CO  and  hydroxyl  Oil  act  separately;  the  formula  which 
represents  most  of  these  facts  is: 

CH3-CO-OH,  or  CH3,  COOH. 

580.  A  radical  is   simply  the  residue  which  is  left  of 
a  body  after   undergoing  a  chemical   change.     Thus  we 

*  In  the  following  chapters  the  ethane,  C2,  compounds  will  be  taken  when 
possible,  partly  because  they  are  better  known,  and  partly  to  accumulate 
examples  to  familiarize  the  student  with  organic  transformations.  He  must 
keep  constantly  in  mind  that,  caeteris  paribus,  analogous  facts  are  true  of 
similar  bodies,  Na  and  K;  Cl  and  Br;  O  and  S;  P  and  As;  (CH3)',  (CaII5)', 
and  (C6H5)';  or  CH2OH,  and  CH2SH. 


ISOMERISM.  293 

may  believe  from  the  foregoing  that  acetic  acid  contains 
basic  and  acid  hydrogen,  H,  hydroxyl,  OH,  carbonyl, 
CO,  carboxyl,  COOH,  methyl,  CH3,  and  acetyl,  C2H3O, 
because  each  one  of  these  can  be  exchanged  for  or  com- 
bined with  other  radicals  or  the  elements,  although  no 
one  of  them  has  been  isolated  except  CO  in  carbonous 
oxide. 

ISOMERISM. 

581.  Two  or  more  compounds  which  contain  the  same 
elements,  and  have  the  same  percentage  composition,  but 
differ  in  properties,  are  said  to  be  isomeric.  There  are 
several  varieties  of  Isomerism: 

1.  Bodies  arc  physically  isomeric  when  they  differ  only 
in  certain  physical  properties,  as  their  odors  or  their  re- 
lation to  polarized  light.     Over  twenty  volatile  oils  have 
the  composition,  C101I16    (lemons,  orange,  bergamotte). 

2.  Bodies  are  isomeric  in  the  strict  sense  of  the  word 
when  they  have  the  same  vapor  density,  the  same  per- 
centage composition,  and  exhibit  similar  chemical  changes 
under  similar  circumstances.     Thus   there  are  two  pri- 
mary butyl  alcohols  which  are  strictly  isomeric: 


CH3  CH2-CH2-CH2OH,  and         »  >CII-CH2OH, 

3 

and  which   give  rise  to  other  compounds,  acids,  ethers, 
etc.,  which  are  also  isomeric. 

3.  In  the  general  use  of  the  word,  metameric  bodies 
are  also  called  isomers.  Bodies  are  metameric  when  they 
have  the  same  percentage  composition  and  the  same 
molecular  weight,  but  exhibit  dissimilar  chemical  prop- 
erties under  similar  circumstances. 

Propionic  acid,  methyl  acetate,  and  ethyl  formate  have  the  same 
molecular  formula,  C3H6O2,  but  when  acted  upon  by  caustic  potash 
yield  very  dissimilar  products: 

The  first,  water  and  potassium  propionate, 


294  ORGANIC  CHEMISTRY. 

CH3  •  CH2    COOH  +  KOH  =  H2O  -f  CH3    CH2    COOK  : 
the  second,  methyl  alcohol  and  potassium  acetate, 

CH3-  O-C2H3O-f  KOII  =  CH,OH  + CH3COOK: 
the  third,  ethyl  alcohol  and  potassium  formate, 

C2H5O    O-  CIIO  +  KOH  =  C2H5OH-fH,  COOK. 

These  reactions  point  to  differences  of  structure  within  the  molecules, 
which  are  approximately  represented  by  formuhe  like  those  above. 

Sonic  metamers  arc  so  totally  different  that  no  resem- 
blances of  structure  have  been  imagined  to  exist.  Such 
are  starch  and  gum  arable,  which  are  pseitdo-isomers. 

Metamers  are  found  in  all  terms  above  C3,  and  in- 
crease in  number  very  rapidly  with  each  addition  of 
CII2.  There  are  four  butyl  alcohols  known,  two  pri- 
mary, which  are  strictly  isomeric  with  each  other,  and 
two  others  metameric  with  these,  which  do  not  form 
corresponding  acids  and  ethers. 

4.  Polymeric  bodies  agree  in  percentage  composition, 
but  do  not  have  the  same  molecular  weight.  Their 
formula?  are  multiples  of  some  empirical  formulae  com- 
mon to  all,  as  the  CII2  in  the  olefines,  C,,H,n. 

582.  There  are  more  than  twenty  compounds  which 
yield  on  analysis  C,39.82%,  H,6.75#,  O,53.43^,  corre- 
sponding to  the  empirical  formula,  C1I2O.  The  follow- 
ing table  gives  some  of  them: 


CH2()       =      H  •  CIIO,  formic  aldehyde. 

CH3  •  O  •  CHO,  methyl  formate. 

CH3-  COOH,  acetic  acid. 

(H  •  CHO) 3,  para  formic  aldehyde. 

CH3    O    CH2    COOH,  methyl  glycollic  acid. 

CH3    CHOH,  COOH,  ethylidene  lactic  acid. 

CH2OH  •  CH2-  COOH,  ethylene  lactic  acid. 
C4H8O4         —  erythrite  aldehyde? 
C5H10O5        —wanting. 


-{ 

C3H603 


ISOMERISM.  295 

f  (HCHO)6,  nieta  formic  aldehyde. 

C6H12O6  =  |  CH2OH(CHOH)4CHO,  glucoses    dextro  and  Isevo. 
1  C6H6(OH)6,  phenose. 

The  groups  (CH2O)n  are  polymeric  with  each  other;  the  three 
aldehydes  are  stictly  polymeric.  The  members  of  each  group  are 
isomers  in  the  general  sense.  Some  are  strictly  isomeric,  as  the  two 
lactic  acids,  and  some  are  metamwic,  as  a  lactic  acid  and  methyl 
glycollic  acid. 

There  are  also  two  modifications  of  ethylidene  lactic  acid  which 
contain  the  same  radicals,  and  are  chemically  identical,  but  they 
difler  in  their  relations  to  polarized  light,  and  are  physical  isomers. 
The  chemical  structure  of  these  molecules  is  the  same,  but  the 
molecules  have  a  different  arrangement  among  themselves. 


CLASSES  OF  ORGANIC  COMPOUNDS. 

583.  The   hydrocarbons   contain    carbon  and    an   even 
number  of  hydrogen  atoms.     They  include  the  paraffins, 
olefines,  benzenes,  and  representatives  of  a   dozen   other 
series.      It    is    sometimes   convenient    to   write   them   as 
hydrides;    that   is,   as   having   replaceable   hydrogen,   as 
C2H5-H,  ethyl   hydride,  but   more  frequently  as   made 
up  of  compound  radicals  called  alkyls,  as 

CH3-CH3=  dimethyl. 

584.  The  alcohols  are  hydroxides  of  these  hydrocarbon 
radicals,  formed,  as  may  be  supposed,  from  the   hydro- 
carbons by  the  substitution  of  hydroxyl  for  hydrogen,  as 
ethyl  hydroxide;C2H5OH,  from  ethyl  hydride,  C2H5-H. 
The  methyl  or  "carbinol"  series  of  alcohols  contain  but 
one  hydroxyl  group,  as   the  ordinary  or  ethyl  alcohol, 
C2H5OH.      Such    alcohols    are    monohydric.     There    are 
other    series    of  alcohols    which    contain    two,   three,  or 
more    hydroxyl   groups.     Dyad    radicals   yield    dihydric 
alcohols,  or  glycols,  as  C21I4(OH)2,  ethene  glycol;    and 
triad    radicals,   the    trihydric    glycerols,   as    C3H5(OH)3, 


296  ORGANIC  CHEMISTRY. 

commonly  known  as  glycerine.  The  London  Chemical 
Society  recommends  that  all  alcohols  take  the  termina- 
tion ol. 

585.   The  normal   alcohols  take  their  names  very  gen- 
erally from  those  of  the  radicals  given  on  p.  21)1,  as 

methyl  alcohol,  C  II 4  O  =  ("'  II 3  OH  =  1I.C1I0()II. 
ethyl  alcohol  C2II6  O  =  C21I5  OII  =  C  H3  CH2OH. 
propyl  alcohol,  C3"lI8  O  =  C8H7  OU  =  C,,I15  Cll.OH. 
butyl  alcohol,  C4H10O  =  C4H9  OH=C8H7  CH2OH. 
amyl  alcohol,  C5H12O  =  C5H11OH  =  C4H9'CH2OH. 
hexyl  alcohol,  06II14O  =  C6II18OII  =  C5lll ,-CH2OH. 

The  first  two  alcohols  have  no  isomers  ;  propyl  has  two; 
butyl,  four;  after  this  the  numbers  of  alcohols  theoret- 
ically possible  increase  very  rapidly,  being  for  amyl  8, 
hexyl  17,  heptyl  30,  octyl  78. 

The  isomeric  alcohols  present  many  points  of  peculiar 
interest,  and  are  divided  into  three  classes. 

1.  The  primary  alcohols,  which  may  be  oxidized,  first, 
to  aldehydes,  and  then  to  acids,  which  contain    the  same 
number   of  carbon   atoms.     These  alcohols  are  supposed 
to  contain  the  monovalent  radical,  CII2OII,  as  a  terminal 
group,  t.  g.,  normal  butyl  alcohol, 

CH3  CH2  CH2-CH2OH. 

2.  The   secondary  alcohols   are   supposed   to   contain   a 
divalent  radical,   CHOH,  e.  g.,  secondary  butyl   alcohol, 
CH3-CHOH-C2H5.     Oxidizing  agents  convert  this  rad- 
ical to  CO.  and  the  alcohol  to  a  ketone,  as  methyl  ethyl 
ketone,  CH3-CO-C2H5. 

3.  The  tertiary  alcohols,  when  oxidized,  are  completely 
broken  up,  yielding   neither  aldehydes  nor  ketones,  but 
two  acids  containing  each  a  less  number  of  carbon  atoms. 
These    are    supposed    to    contain    the    trivalent    radical, 
=COH,  united    to   three  other  carbon  atoms,  as   in  ter- 
tiary butyl  alcohol. 


CLASSES  OF  ORGANIC  COMPOUNDS.  297 


>COH-CH3,  or  CH8,  CH3-COH-CH3. 

NOTE.  —  A  comma  placed  between,  two  radicals  indicates  that  both 
are  equally  joined  to  the  following  group.  The  dot  (or  dash)  in- 
dicates that  they  are  joined  to  each  other. 

586.  The  different  behavior  of  these  alcohols  upon  oxi- 
dation is  due  to  three  different  class  radicals,  (CH2OH)', 
(CHOH)",  and  (COH)'"  ;  but  there  are  also  other  dif- 
ferences resulting  from  the  structure  of  the  nuclei.     Nor- 
mal alcohols  are  those  in  which  no  carbon  atom  is  more 
than   doubly  united   to  another  carbon   atom,  as   normal 
butyl    primary    alcohol,    CH3-  CH2  CH2-  CH2OH.     The 
150   alcohols   have   at   least  one   carbon   atom   united    to 
three  other  carbon  atoms  ;  as,  isobutyl  primary  alcohol  : 

CH3>CH   CH2°H  or  CH8,  CHg-CH-CHjOH. 

587.  Many  organic  acids  are  formed  by  the  oxidation 
of  the  primary  alcohols;  the  radical  CH2OH  becoming 
COOH.     The  primary  "  methyl  ''  alcohols  give  rise  to  the 
"  fatty"  acids;  as 

C  H2  O2  formic  acid,        C  H  O  •  OH  or  H    COOH. 
C2H4  O2  acetic  acid,         C2H3O    OH  or  C  H3-  COOH. 
C3H6  O2  propionic  acid,  C3H5O    OH  or  C2H5-  COOH. 
C4H8  O2  butyric  acid,      C4H7O    OH  or  C3H7    COOH. 
C5H10O2  valeric  acid,       C5H9O    OH  or  C4H9    COOH. 

CBH2BOa    general  formula,  CnH2H-iO    OH  or  CnH,n+i-  COOH. 

The  formulae  in  the  second  column  represent  that  hydroxyl  is 
united  to  an  acid  radical;  as,  formyl,  CHO,  acetyl,  C2H3O,  etc. 
Those  in  the  third,  that  carboxyl,  COOH,  is  united  to  an  alkyl 
radical;  as,  CH3,  C2H5,  etc. 

588.  The  aldehydes  are  the  first  products  obtained  by 
oxidizing  the  primary  alcohols;  as, 

=  ethyl  aldehyde. 


298  ORGANIC  CHEMISTRY. 

They  arc  unstable  bodies,  readily  changing  to  the  corre- 
sponding acids;  as, 

C1I3  •  IIC  :O  +  O  =  CH,  •  COOH  =  acetic  acid. 

In  the  aldehyde  radical,  the  carbon  is  directly  united 
both  to  the  hydrogen  and  to  the  oxygen. 

589.  In  the  ketones  the  group  (CO)"   links  together 
two    univalent    alkyl    radicals    which    may    be    the    same 
or    different;    as,   acetone,   CH3  •  CO    Cli3.    methyl-ethyl 
ketone,    CII3   CO  •  ('.,11 ..       The    ketones    are    generally 
obtained  by  the  destructive  distillation  of  the  lime  salts 
of  the  fatty  acids:   (C12H3O2)2Ca=eaCO84-(CH3)2eO= 
acetone,  but  also,  by  the  oxidation  of  the  secondary  al- 
cohols , 

[J'>ciioii  +o  =  H2<H     !!;5>co 

i.     11  3  11    ;f 

Isopropyl  alcohol.  Acetone. 

The  ketones  are  analogous  to  the  aldehydes,  and  every 
ketone  has  some  aldehyde  metameric  with  it,  as  acetone 
is  metameric  with  propyl  aldehyde  (  C2II  -  •  CO  •  II). 

590.  The  ethers  include  .several  classes  of  alkyl  deriva- 
tives. 

1.  All  alcohols  exchange  their  hydroxyl  for  chlorine, 
bromine,  or  iodine,  and  form  haloid  ether*,  which  are 
primary,  secondary,  and  tertiary,  like  the  alcohols  from 
which  they  derived,  as  the  four  butyl  iodides,  C4H9I: 

CH3-cn2  cn0  cnj;          cn3  cn0  cm-cnr 

CH8,CH8-CI-CHa;  CII,.  CII3  CH-CHJ. 

O  •  *>  O    "  O  '  "J  *• 

With  these  are  usually  grouped  the  cyanogen  ethers,  as 
C2II-CN,  ethyl  cyanide.' 

NOTE.  —  The  tertiary  alcohol  radical  COH,  contains  hydroxyl, 
and  is  trivalent.  The  radical,  formyl  IICO,  contains  no  hydroxyl, 
and  is  identical  with  the  aldehyde  radical,  which,  however,  is  not 
formyl.  Compare  formic  acid,  II  •  CO  •  OIL 


CLASSES  OF  ORGANIC  COMPOUNDS.  299 

2.  The  simple  ethers  are  formed  by  removing  one  mole- 
cule of  water  from  two  molecules  of  an  alcohol :  as, 

2(C2H5OH)  —  H2O  =  C2H5-  O  •  C2H5  =  ethyl  ether. 

they  contain   two  similar  alcohol  radicals  united   by   a 
linking  oxygen  atom. 

3.  The  mixed  ethers  contain  two  different  alcohol  radi- 
cals united  by  oxygen ;  as, 

CH3  O    C2H5  =  methyl-ethyl  ether. 

The  simple  and  mixed  ethers  are  anhydrous  oxides  of 
the  alcohol  radicals.  There  are  also  sulphur  ethers,  etc.  ; 
as,  C2H5-  S  •  C21I5,  ethyl  sulphide. 

4.  The  substances  commonly  known  as  compound  ethers 
contain   both  an  acid  and  an  alcohol  radical  linked  by 
oxygen;  as, 

C2H5- O -C2H3O —  acetic  ether,  or  ethyl  acetate. 

They  are  ethereal  salts,  and  may  be  produced  by  the  ac- 
tion of  the  oxy-acids  upon  the  alcohols;  as, 

C2H5OH-f  NOOH  =  H2O+C2H5-O-NO=:ethyl  nitrite. 

All  compound  ethers  are  easily  broken  up  into  alcohol 
and  acid  by  heating  them  with  wrater:  more  easily  in  the 
presence  of  a  strong  base  like  the  alkalies  ;  as, 

C2H5-  O  •  C2H3  O  +  KOH  =  C2H5OH  +  CII3COOK. 

This  process  is  called  saponification,  a  term  originally 
applied  in  the  manufacture  of  soap  from  neutral  fats, 
which  are  compound  ethers  of  glycerine. 

591.  The  metals  also  combine  with  the  alkyl  radicals; 
as,  Zn(CH3)2,  zinc  methide  obtained  by  heating  methyl 
iodide  with  zinc,  2CH3I  -f  2Zn  =  ZnI2  4-  Zn(CH3)2. 
These  must  be  distinguished  from  the  alcoholates  ob- 
tained by  dropping  sodium  or  potassium  into  absolute 
alcohol  C2H5OH-f  Na  =  H-f  C2H5ONa. 


300  ORGANIC  CHEMISTRY. 

592.  The  ammonia  derivatives  have  already  been  men- 
tioned on  page  130. 

The  organic  amines  contain  alkyl  radicals  in  place  of 
one,  two,  or  all  of  the  hydrogen  atoms  in  ammonia. 
Accordingly  they  form  primary,  (N1I)2'  ;  secondary, 
(Nil)";  and  tertiary,  (N)"'  amines;  as, 

Primary.  Secondary.  Tertiary. 

fC2H5 

N     II 

n          In  il 

Ammonia.         Ethyl  amine.         Diethyl  amine.     Triethyl  amine. 

All  amines  strongly  resemble  ammonia  in  odor,  in 
alkaline  reaction,  and  in  basic  character.  They  unite 
directly  with  acids;  as, 

K(C2II5)3IIC1,  triethyl  ammonium  hydrochloride, 
and  also  form  hydroxides  ;  as, 

N(C21I5)4OII,  tetrethylammonium  hydroxide, 

which  are  even  more  stable  and  caustic  than  ammonium 
hydroxide,  NII4OII. 

593.  The  amides  are  also  derived  from  ammonia,  but 
by  substitution  of  an  acid   radical    for  a  part  of  its  hy- 
drogen.    They   also   form    three   classes  —  primary,   sec- 
ondary,   and    tertiary  —  according  as   £,   |,   or   |    of  the 
hydrogen  has  been  removed  ;  as,    - 

MI  C2II30  C2H30  C2II30 


N  <  II        N  <  II  N<  C2H30        N<  02H30 

III  UI  ill  io2II30 

Ammonia.     Acetamide.  Diacetamide.  Triacetamide. 


The  primary  amides  have  a  feebly  basic  character  ;  the 
others  are  feebly  acid. 

The  alkalamides  are  secondary  and  tertiary  ammonia 


ACTION  OF  CHEMICAL  RE-  AGENTS.  301 

derivatives,  containing  both  positive  and   negative  radi- 
cals, as  ethyl  acetamide,  N(C2H6),  (C2H3O)^  H. 

594.  It  will  readily  be  seen  that  an  enormous  number 
of  these  compounds  may  be  formed,  and  also  that  there 
can  not  fail  to  be  numerous  isomers.  Thus,  the  empir- 
ical formula,  NC3H9,  represents  four  isomers,  which  are 
good  examples  of  the  value  of  structural  formula)  : 


CH2-CH2-CH 


UI 

Propylamine. 

fC2H5 


UI 

Ethyl-methyl-amine.  Tri-mcthyl-amine. 

595.  The  imides  are  secondary  amides  containing  imi- 
dogen,  (Nil)"  united  to  a  diatomic  acid  radical,  as:  suc- 
cinimide,  C2H2O-  NH-C2II2O. 

Tlie  nitriles  contain  trivalent  nitrogen,  united  to  a  tri- 
valent  hydrocarbon  radical,  as  CH.  The  first  of  these 
is  methenyl  nitrile,  CH  =  N,  which  has  the  same  empir- 
ical composition  as  prussic  acid,  II,  CN. 

ACTION  OF  CHEMICAL  RE-AGENTS. 

596.  The  number  and  variety  of  organic  compounds  is 
amazing,  and  it  is   almost  impossible   to  describe  them 
without    a    wearisome    monotony.     The    series   differ    in 
marked  peculiarities;  but  the  members  of  any  series  dif- 
fer  gradationally,  being,  as   a   rule,  progressively  gases, 
liquids,  and   solids,  normally  increasing  in    density  and 
also  in  boiling  and  in  melting  points.     Those  of  the  same 
group  resemble  each   other  in  physical  properties,  like 
taste,  odors,  etc. 


302  ORGANIC  CHEMISTRY. 

597.  Many  organic  compounds  may  be  distilled  or  sub- 
limed unchanged,  as  ether,  oxalic  acid.     At  high  temper- 
atures  they   usually   decompose;    sometimes  with   simple 
reactions;  as,  oxalic  acid,  2(COOII)2,  strongly  heated  — 
II2O  -f  CO  -f  2CO2  +  II,  COOII  =  formic  acid.    Generally 
they  yield  a  variety  of  complex  products  and  a  residue 
of  coke.     Heated   in   the  air  they  undergo  the  changes 
of  ordinary  combustion. 

598.  The  usual  re-agents  produce  in  organic  bodies  the 
ordinary  combinations,  substitutions,  and  double  decom- 
positions,  and    always    in    accordance    with    the    law    of 
equivalent  valency. 

The  oxygen  of  the  air,  at  ordinary  temperatures,  has  little  effect 
upon  most  saturated  organic1  compounds.  Unsaturated  compounds, 
like  aldehydes  and  weak  aqueous  solutions  of  the  alcohols,  rapidly 
oxidize.  The  influence  of  oxygen  in  putrefaction  and  fermentation 
will  he  considered  in  another  place.  Moderate  oxidation  of  organic 
bodies  is  effected  by  nascent  oxygen  usually  obtained  by  mixtures 
of  sulphuric  acid  with  poiassium  bichromate  (CHROMIC  MIXTURE), 
or  with  manganese  dioxide.  The  caustic  alkalies  and  moist  silver 
oxide  are  excellent  oxidizing  agents  for  the  aldehydes  and  the  poly- 
hydric  phenols. 

Ordinary  nitric  acid  is  used  as  an  oxidizing  agent,  or  like  any 
other  acid,  to  form  salts  and  ethers.  The  fuming  acid  acts  often 
witb  great  violence  upon  organic  bodies,  forming  substitution  prod- 
ucts in  which  the  radical  nitryl  (NO2)' replaces  hydrogen,  as  ben- 
zene =  C6Hfi  -f  HNO3  =  II2O  +  C6II5NO2  =  nitrobenzene.  Such 
nitro  substitution  compounds  are  converted  by  nascent  hydrogen  to 
amines,  as  C6H5NO2  +  H6  =2H2O  +  C6H5NII2  =  aniline. 

599.  Oxygen  compounds  may  lose  the  elements  of  water, 
irOII,  when  heated  with  P2O5,  ZnCl2,  or  with  strong 
H2S04,  as  C2II.OH  +  H2S04=II2S04-j  II20+C2H4. 
Conversely  a  prolonged  boiling  with  weak  sulphuric  acid 
causes  the  assumption  of  water,  as  cane  sugar, 

C^H^On +H20is  changed  to  2C6H12O6  —glucose. 

600.  Nascent  hydrogen   is  obtained  in  acid  mixtures 


ACTION  OF  CHEMICAL  RE-AGENTS.  303 

from  Zn-f-H2SO4,  or  on  the  larger  scale  from  iron  fil- 
ings and  acetic  acid  ;  in  alkaline  mixtures,  from  sodium 
amalgam.  It  acts  reducing. 

601,  Free  chlorine  and  bromine  act  energetically  upon 
organic  compounds. 

(1)  Removing  hydrogen  without  replacement, 

C2H5OII  +  C12  =  2IIC1  +  C2H4O  =  aldehyde. 

(2)  also  replacing  it,  CII3COOII  +  C12  =CH2C1,  COOH  +  IIC1 ;  and 

(3)  by  direct  addition,  C2H4  -f-  C12  =  C2H4C12  ;  (4)  in  presence  of 
water  also  acting  oxidizing,  II2O  -f  C12  =2HC1  -f  O. 

Iodine  is  less  energetic,  generally  requiring  the  presence  of  a 
third  body  (as  phosphorus)  to  form  substitution  products.  So  also 
hydriodic  acid  is  somewhat  different  in  action  from  either  hydro- 
bromic  or  hydrochloric  acid. 

602.  The  chemical  changes  by  which  a  body  is  trans- 
ferred from  one  series  to  another  are  always  interesting 
and  frequently  of  great  importance.     The  following  ex- 
ample is  worthy  study:    (1)  Marsh  gas,  CH4,  acted  upon 
by   Cl  in   the   sunshine,  yields   CH3C1   methyl   chloride. 
(2)  CH3C1,  distilled  with  KOH,  yields  KC1,  and  CH8OH= 
methyl    alcohol.       (3)     CH3OH,    distilled    with    strong 
H2SO4,    yields    (CH3)2    SO4  =  methyl    sulphate.       (4) 
(CH3)2   SO4,  distilled   with   KCN,  produces  2(CH8CN) 
methyl  cyanide.     (5)  This  is  identical  with  aceto  nitrile 
C2H3N,  a  molecule   containing  two  carbon  atoms,  and 
which,  when  acted  upon  by  nascent  hydrogen,  becomes 
C2H5NH2  ethyl  amine.     (6)  Nitrous  acid  converts  the 
amines    to    the    corresponding   alcohols;    in    this   case  to 
C2H5OH  ethyl  alcohol.     (7)  Ethyl  alcohol,  by  oxidation, 
yields  C2H4O  aldehyde,  and   C2H4Q2   acetic  acid.     (8) 
Calcium  acetate  roasted  yields  acetone  C3H60,  with  three 
carbon  atoms,  etc.,  etc. 

This  example  also  shows  how  the  chemist  may  pass  from  one 
carbon  compound  to  the  next  higher  in  the  same  series,  as  from 


304  ORGANIC  CHEMISTRY. 

methyl  to  ethyl  alcohol ;  and  it  will  be  readily  understood  that 
other  products  belonging  to  other  series  may  as  readily  be  obtained. 
We  shall  now  enter  upon  a  study  of  some  of  the  substances  which 
are  found  in  the  various  classes  of  organic  compounds,  neither  at- 
tempting nor  desiring  to  give  so  much  as  the  names  of  the  greater 
part  of  them.  The  selection  which  has  been  made  contains  those 
bodies  which  the  student  is  likely  to  meet  in  his  daily  life. 

As  a  rule  only  one  process  has  been  given  for  preparing  these 
compounds,  and  that  one  generally  selected  for  its  theoretical  im- 
portance rather  than  for  its  commercial  value.  In  very  many  cases 
there  are  a  dozen  different  processes  for  reaching  the  same  result. 


Recapitulation. 

(1)  A  carbon  atom  is  tetravalent,  and  is  capable  of  combining  with 
other  carbon  atoms. 

(2)  The  hydrocarbons  are  typical  compounds.     Those  containing  an 
odd    number  of   hydrogen    atoms   must   be   radicals ;    the  others 
may  be,  except  the  paraffins. 

(3)  From  these  radicals   may  be  formed  homologous  series,  like   the 
alcohols,    the   acids,    the   ethers,   etc.,    whose   members    undergo 
the  same  kind   of  chemical    transformations,  but   differ  grada- 
tionally  in  their  properties. 

(4)  These   series  are   characterized    by   a   common   "class"  radical, 
as  OH  in  acids,  alcohols,  and  phenols,  COOH  in  acids,  CH2OII 
in  primary  alcohols,  NII2  in  amides,  or  by  a  linking  bond,  as 
O  or  8  in  ethers,  CO  in  aldehydes  and  ketones. 

(5)  In  any  series  are  members  with  isomeric  modifications,  which 
exhibit  various  degrees  of  similarity  from  the  almost  identical 
to  a  mere  agreement  in  percentage  composition. 

(6)  The  isomers  are  supposed  to  be  due  (1)  to  a  difference  in  the 
class  radical,  or  (2)   in  the  nucleus,  or  (3)  to  a  difference  in 
the  physical  arrangement  of  the  molecules. 

(7)  Chemical  forces  produce  in  organic  compounds  the  same  changes 
as  in  inorganic,  except  that  the  range  is  wider. 

(8)  Any  compound  of  carbon  may  be  divided  into  two  radicals  of 
equal  valency,  which  are  residues  of  chemical  reactions. 

(9)  That  structural  formula  of  a  compound  is  most  valuable  which 
represents  the  largest  number  of   chemical   transformations  of 
the  given  compound. 


CHAPTER    XVIII. 

CYANOdEN    COMPOUNDS. 

603.  Cyanogen  gas  was  isolated  by  Gay  Lussac,  in  1815. 
It  has  a  molecular  density  of  26,  and  being  composed 
only  of  carbon   and   nitrogen,  must   have  the  molecular 
formula,  C2N2(12x2  +  i*x2).  It  is  interesting,  as  being  the 
first  example  discovered  of  the  existence  of  a  free  radi- 
cal, which    is   in    this    instance    the    monovalent   radical 
cyanogen  •  CEEN  or  Cy. 

Cyanogen  compounds  are  of  frequent  occurence  in  Nat- 
ure, being  easily  obtainable  from  the  leaves  and  kernels 
of  stony  fruited  plants,  like  peaches  and  plums;  as, 
HCN,  prussic  acid  ;  and  even  from  the  human  saliva, 
as,  KCNS,  potassium  sulphocyanate.  Potassium  cyanide, 
KCN,  is  sometimes  found  in  hearths  of  iron  furnaces 
that  use  charcoal  as  fuel,  being  formed  at  high  tempera- 
tures by  the  union  of  the  nitrogen  of  the  air  blast  with 
the  carbon  of  the  fuel  and  its  potassium. 

The  same  compound  may  be  obtained  by  heating  any 
nitrogenous  body,  like  dried  albumin,  with  a  pellet  of 
potassium.  If  the  roasted  mass  be  dissolved  in  water, 
filtered  and  treated  when  cold  with  a  few  drops  of  fer- 
rous sulphate,  partially  changed  to  a  ferric  salt,  and  then 
neutralized  with  HC1,  a  precipitate  of  Prussian  blue  will 
be  formed  which  contains  Fe7(C3N3)6.  This  reaction  is 
a  very  delicate  test  for  nitrogen  in  such  organic  bodies. 

604.  Potassium  ferrocyanide  is  manufactured  by  fusing 
together  dried  animal  matters,  such  as  scraps  of  leather, 
horn   parings,  etc.,  with   potassium   carbonate,  and   iron 
filings.     The  fused  mass  is  cooled,  then  lixiviated  with 

Chem.— 20.  (  305 ) 


306  ORGANIC  CHEMISTRY. 

hot  water.  On  evaporating  this  solution,  the  salt  crystal- 
lizes out  in  yellow  quadratic  prisms,  K4  FeC6N  0  -4-3H2O. 
This  is  the  most  convenient  source  for  obtaining  other 
cyanogen  compounds. 

I.  Strongly    heated    alone   it   decomposes,  yielding   po- 
tassium cyanide,   K4Fc<\.N0  —  ^2  "f  *V^'  -f  4KCN. 

II.  Strongly  heated  with  potassium  carbonate,  it  yields 
potassium  cyanide,  KCN;  mixed  with  potassium  cyanate, 
Kl'NO;  thus, 

K4Fi'(C8Na)2  -|-  K2COS  =  0>2   !   Fo  f  5KCN  -f  KCNO. 

III.  This  product,  by  remelting  with  oxidizing  agents, 
yields  pure  potassium  cyanate  ;  r.  '/.. 

4KCN  -I-  Pl>3<>4    --Ph.,    ;-  4KCNO, 

or  (2)  with  reducing  agents,  like1  charcoal,  yields  pure 
potassium  cyanide,  KCNO  ,  -C  -  (X*)  -[  KCN,  or  (II)  if 
heated  with  strong  sulphuric  acid,  yields  hydrocyanic 
acid  itself,  2(  K4  Fe((13N3 ),)  -f  :iII2SO4  - 

K ,  Fe2((  \, X 3  )2  -|-  3K 2S04  -f  (;I1"CN: 

Jt  is  advisable  to  moderate  the  action  by  the  addition  of 
about  20  parts  of  water.  Tlie  hydrocyanic  acid  which 
forms  may  then  be  distilled  over,  mixed  with  water.  Ex- 
ceediny  care  must  be  used  in  its  preparation,  the  receiver 
cooled  with  ice,  and  any  uncondensed  vapors  completely 
carried  away  from  the'  operator  by  a  strong  draught. 

605.  Anhydrous  hydrocyanic  acid,  II ON,  is  a  clear 
liquid,  boiling  at  2(»°0,  congealing  at  — 15°:sp.  gr.  0.7. 
It  decomposes  spontaneously  after  a  time,  evolving  odors 
of  NII3.  Its  aqueous  solution  is  more  stable;  but  even 
this,  when  boiled  with  acids  or  alkalies,  is  rapidly  de- 
composed, yielding  formic  acid  and  ammonia, 

ITCN-f  2H2Q-f-IICI  =  H,  COOH-f-NII3,  IICl. 
The  officinal  solution   of  the  apothecary  contains  2^ 


CYANOGEN  COMPOUNDS. 


307 


of  the  anhydrous  acid,  and  has  an  odor  resembling  that 
of  bitter  almonds.  In  this  dilute  condition  it  is  a  valued 
medicine.  The  greatest  caution  is  necessary  in  hand- 
ling it,  as  it  is  one  of  the  most  violent  poisons  known;  a 
single  drop  of  the  anhydrous  acid  being  sufficient  to 
cause  death  almost  instantaneously.  The  metallic  cyan- 
ides also  yield  1ICN  when  treated  with  a  dilute  acid, 
and  hence  are  often  as  poisonous  as  the  acid  itself. 

606.  The  metallic  cyanides  arc  obtained  by  the  action 
of  hydrocyanic  acid  upon  their  oxides.     The  simple  cy- 
anides are  analogous  to  the  chlor- 

ides, the  radical  ON  or  Cy  exactly 
taking  the  place  of  an  atom  of 
chlorine  ;  e.  g., 

HgO-{-2IICl   :=H2O-f-ITgCl2. 
HgO  +  2IICN  =  II2O  +  HgC2N2. 

607.  Cyanogen    gas,    C2N2,    is 
formed  when  dry  mercuric  cyanide 
is  strongly  heated.     It  is  a  color- 
less, very  poisonous  gas,  which  has 
the  odor  of  prusstc  acid,  and  burns 
with  a  fine  peach-colored  flame.     It 
has  a  density  of  1.86.     It  is  easily 
condensed  to  a  colorless  liquid,  sp. 
gr.    0.8G,    which    boils    at   --21°C, 

and  freezes  to*  a  crystalline  mass  at  —  34°C.  Cyanogen 
gas  passed  into  a  solution  of  potassium  hydrate  yields 
potassium  cyanide  and  potassium  cyanate: 


C2N2 


The  radical  cyanogen  is  characterized  by  a  great  tendency  to 
form  polymeric  compounds.  Some  are  saturated,  as  cyanogen  gas 
and  paracyanogen,  a  brown  substance,  which  forms,  along  with 
cyanogen,  when  HgC2N2  is  heated.  Others  are  complex  radicals; 


FIG.  101. 


308  ORGANIC  CHEMISTRY. 


Divalent,  C2N2  =          ~^      ;  trivalent,  C3N3--     N  —  C 


There   are   also   metameric  compounds  in  which   the   nitrogen    acts 
pentavalent;  as,  iso-cyanogen  and  its  polymers: 

CE=N-  R,  isocyanide;  divalent,  C~N     R;  etc. 

R     N  ^:  C 

and  pseudo-cyanogen  and  its  polymers,  in  which  the  C  and  X  are 
linked  by   two  bonds,  as  in  potassium  cyanate, 

K  •  N  •  C  =  () 

K-N  =  C  =  O,  cyanate;  divalent,  _  etc. 

O  =  C  •  X  •   K 

There  are  also  compounds  of  carbon   and   nitrogen,  which  contain 
two  different   forms  of  these. 

Moreover,  compounds  based  on  these  Ixxlies  readily  change  one 
into  the  other,  and  quite  as  readily  decompose;  the  nitrogen  pro- 
ducing ammonia;  the  carbon,  formic,  oxalic,  and  other  acids. 

608.  Potassium  cyanide,  KCX,  forms  colorless  cubical 
crystals,  deliquescent,  easily  soluble  in  water,  and  exhal- 
ing the  odor  of  hydrocyanic  acid.  This  dilute  solution 
rapidly  decomposes  to  potassium  formate  and  ammonia, 
KCN4-2H2O  =  NH8-fH-COOK.  Heated  with  the  me- 
tallic oxides  it  melts  easily,  forming  a  tine  flux,  and  also 
acts  as  a  strong  reducing  agent,  becoming  itself  oxidized 
to  cyanate,  PbO  +  KCX  =  Pb  +  K  •  CX  •  O. 

The  other  alkaline  cyanides  resemble  KCX.  The  cy- 
anides of  the  heavy  metals  (except  mercuric  cyanide, 
IIgC2X2)  are  insoluble  in  water,  and  may  be  prepared 
by  mixing  solutions  of  their  salts  with  a  solution  of 
KCX,  avoiding  an  excess.  The  most  important  are 
AgCX,  XiC2N2,  AuC3X3. 

If  an  excess  of  KCX  is  used,  most  cyanides  of  the 
heavy  metals  unite  with  it  to  form  double  cyanides, 
which  are  easily  soluble  in  water;  as, 

AgCX,  KCX^Ag-C=X 

N  =  C    K. 


CYANOGEN  COMPOUNDS.  309 

These  double  cyanides  are  easily  decomposed  by  HC1, 
forming  chlorides  of  the  metals  and  setting  free  HON. 
They  are  therefore  poisonous.  They  have  been  exten- 
sively used  in  electroplating,  because  they  yield  by  elec- 
trolysis the  metals  in  strongly  coherent  films. 

609.  The  cyanides  of  iron  are  difficult  to  obtain,  because 
they  so  readily  unite  with  other  cyanides.  In  presence 
of  an  excess  of  KCN,  they  unite  so  intimately  with  it  as 
to  form,  not  double  cyanides,  but  entirely  new  com- 
pounds, in  which  the  iron  does  not  respond  to  the  ordi- 
nary tests,  and  which  do  not  evolve  HCN  on  being 
treated  with  cold  dilute  acids.  The  commercial  manu- 
facture of  one  of  these,  potassium  ferrocyanide,  has  been 
given  in  §  604.  The  other  is  potassium  ferri-cyanide,  pre- 
pared by  passing  chlorine  into  a  cold  solution  of  potas- 
sium ferrocyanide  until  a  drop  of  the  liquid  will  no 
longer  produce  a  blue  precipitate  with  ferric  chloride. 
On  evaporating  this  solution,  potassium  ferri-cyanide, 
K3FeC6N6,  forms  in  ruby  rhombic  prisms: 

2K4FeC6N6  +  C12  =  2KC1  +  2K3FeC6N6. 

The  chlorine  acts  by  removing  a  fourth  part  of  the  po- 
tassium, and  by  converting  the  iron  from  the  ferrous 
(Fe")  to  the  ferric  (Fe'")  state.  The  ferri-cyanide  in 
presence  of  alkaline  hydrates  acts  oxidizing,  and  reverts 
to  ferrocyanide.  This  property  is  utilized  in  calico  print- 
ing, in  which  such  a  mixture  is  used  as  a  discharge  for 
indigo:  2K3FeC6N6+2KHO:=H20  +  2K4FeC6N6  +  0. 
The  former  is  known  as  the  yellow,  and  the  latter  as 
the  red,  prussiate  of  potassium.  The  yellow  prussiate 
is  extensively  employed  in  the  manufacture  of  dyes  and 
paints,  as  Prussian  blue  and  chrome  green.  The  potas- 
sium in  both  these  "prussiates"  may  be  replaced  by  hy- 
drogen or  by  the  metals,  leaving  in  both  cases  a  residue 
of  Fe(C3N3)2,  which,  in  the  former,  acts  as  an  "ous"  rad- 
ical, tetravalent  ferro-cyanogen,  and,  in  the  latter,  as  an 


310  ORGANIC  CHEMISTRY. 

uic"  radical,  the  trivalent  ferri-cyanogen.     Their  struct- 
ural formulae  are  here  contrasted  : 


,X,  •   K 

Potassium  ferrocyanide.  Potassium  ferricyanide. 

The  hydrogen  compounds,  H4Fe(C3N3)2,  hydro-ferrocy- 
anic  acid,  and,  II3Fe(C3X3)2,  hydro-f'erricyanic  acid  are 
unimportant.  They  are  decomposed  l>y  long  boiling, 
yielding,  among  the  products,  prussic  acid,  IICN. 

610.  The  other  ferrocyanides  are  formed  by  mixing  so- 
lutions of  potassium  ferrocyanide  with  those  of  the  other 
metals,  producing  compounds  like  the  cupric  ferrocyan- 
ides, CuK2FeC6N6,  and  CiuFeCyNg.  according  as  an 
excess  of  the  one  or  the  other  solution  is  used.  The  ferri- 
cyanides  are  produced  by  analogous  reactions,  but  ob- 
viously not  in  the  presence  of  bodies  like  SnCl2,  which 
are  easily  oxidized;  nor  in  the  presence  of  strong  alka- 
lies, which  decompose  them. 

Some  of  these  reactions  are  valuable  tests.  Especial 
interest  attaches  to  the  reactions  with  salts  of  iron,  al- 
ready noted  on  page  2G6. 

When  oxygen  is  completely  excluded,  green  ferrous 
sulphate  yields  with  potassium  ferrocyanide: 

Fe"2,  Fe"   (C8N8)2,  and  K2Fe",  Fe"(C3N3)2, 
both  speedily  oxidize  in  the  air,  to  Prussian  blue. 
Fe'"4(Fe"CeN,)8, 

which  forms  immediately  when  ferric  chloride  is  added 
to  potassium  ferrocyanide.  An  excess  of  the  latter  dis- 
solves a  portion  of  this,  forming  the  so-called  soluble 
Prussian  blue. 

With  solutions  of  the  ferri-cyanide,  ferrous  salts  yield 
Turnbull's  blue,  Fe"8(Fe'"C6N6)2.  Ferric  salts  yield  no 


CYANOGEN  COMPOUNDS.  311 

precipitate,  unless  some  reducing  agent  is  present,  when 
a  blue  precipitate  forms. 

These  beautiful  blue  colors  are  employed  extensively 
in  dyeing,  and  in  the  manufacture  of  paints.  The  ordi- 
nary blue  ink  is  Prussian  blue  dissolved  in  oxalic  acid. 

Similar  complex  radicals  containing  Co,  Mn,  Pt,  and  Cr,  in  place 
of  Fe,  are  known.  Of  these,  potassium  cobaltic-cyanide,  K3CoC6NG, 
is  important,  because,  by  forming  it,  a  quantitative  separation  of 
cobalt  from  nickel  may  be  effected.  Cobalt  also  forms  several  series 
of  complex  cyanogen  compounds  which  can  not  here  be  described. 

611.  Nitro  prussides  are  formed  by  treating  the  alka- 
line   ferrocyanides  with    fuming    nitric   acid.     Potassium 
ferrocyanide  so  treated  yields  approximately: 

K4FeC6N6-f3IIN03  = 

Ct)2-f  NH3-[-2KN03  +  K2FeC5N5NO  = 

the  nitro  prusside  of  potassium. 

In  these  compounds  the  radical  nitrosyl  is  exchanged  for 
one  of  cyanogen.  The  soluble  nitro  prussides  are  exceed- 
ingly delicate  tests  for  the  alkaline  sulphides,  with  which 
they  strike  in  dilute  solutions  a  beautiful  purple  color. 

612.  Cyanogen  forms,   with   the   alcohol   radicals,  two 
series  of  ethers;  the  cyanides  or  nitriles,  as  ethyl  cyanide, 
C2H5CN,  and  their  metamers,  the  isocyanides  or  carba- 
mines;  as,  ethyl  isocyanide,  C2H5NC.     These  compounds 
differ   widely   in    their    properties,   and   will    be    further 
considered. 

Cyanogen  also  combines  with  the  halogens,  forming 
cyanogen  chloride,  CNC1,  which  is  a  liquid,  and  its  poly- 
mer, C3N3C13,  which  is  a  solid,  and  other  compounds. 

613.  There  are  two  isomeric  potassium  cyanates;   the 

normal,  obtained  by  passing  the  vapor  of  cyanogen  chlor- 
ide into  potash  lye: 

CN  •  01  +  2KIIO  =  KOI  +  II 2  O  +  (0  =  N)  •  O  •  K. 


312  ORGANIC  CHEMISTRY. 

This  changes,  when  melted,  to  the  usual  form,  which  is 
known  as  the  iso-cyanate,  or  the  pseudo-eyanate  : 


obtained  as  before  noted  by  heating  potassium  cyanide 
with  metallic  oxides.  Only  one  cyanic  acid  is  known, 
CNOH,  probably  the  normal  acid,  N  —  OO-II.  It  has 
several  isomers.  Cyamelide,  a  white  amorphous  mass 
into  which  it  spontaneously  changes.  Cyanuric  acid 
(C3N8)(()II)3,  which,  when  heated,  becomes  cyanic  acid, 
and  fiilminic  acid,  (C0N0)(OII)0,  which  has  never  been 
isolated,  and  fulminuric  acid,  C3N3II3O3,  isomeric  with 
cyanuric  acid,  but  monobasic. 

Ammonium  isocyanate,  CN-O-NII4,  produced  when 
the  dried  vapors  of  cyanic  acid,  CNOH,  and  ammonia, 
NII3,  meet,  is  manufactured  by  decomposing  lead  cyanate 
with  ammonium  sulphate.  This  body  is  remarkable, 
because  it  passes  spontaneously,  even  in  the  solid  state 
(more  rapidly  on  heating  its  solution),  into  urea,  with 
which  it  is  isomeric,  NII2-CO'NII2.  Therefore,  urea  (1) 
can  be  made  from  ammonia  plus  cyanic  acid.  (2)  If 
urea  is  heated,  it  breaks  up  into  ammonia  and  cyanuric 
acid;  but  (3),  if  cyanuric  acid  is  still  further  heated,  it 
splits  up  into  the  original  cyanic  acid. 

614.  The  fulminates  of  silver  and  of  mercury  are  re- 
markable for  the  violence  with  which  they  explode  on 
being  struck.  They  are  used  for  filling  percussion  caps. 
On  the  large  scale,  mercuric  fulminate,  CIIgXO2CX,  is 
made  by  adding  to  one  part  of  mercury  12  parts  of  nitric 
acid  and  6  parts  of  alcohol.  After  the  reaction  begins 
other  6  parts  of  alcohol  are  added  by  degrees.  Vapors 
of  nitric  ether,  aldehyde,  etc.,  are  given  off,  and  the  mer- 
curic fulminate  forms  in  crystalline  plates.  These  are 
purified  by  redissolving  in  hot  water  and  recrystalliz- 
ing.  The  greatest  care  is  necessary  in  handling  the  dry 
salt,  even  in  very  small  quantities. 


CYANOGEN  COMPOUNDS.  313 

Silver  fulminate,  CAg2NO2CN,  is  prepared  in  a  sim- 
ilar manner.  It  is  one  of  the  most  dangerously  explo- 
sive compounds  known. 

615.  Sulphocyanic  acid,  CNSH,  is  the  analogue  of  cy- 
anic acid,  which   it  resembles.     Its  most  important  salt, 
potassium    sulphocyanate,   occurs    in    the   saliva,   and    is 
easily  formed  by  fusing  together  sulphur  and  potassium 
ferrocyanide.     After   cooling,   the   sulphocyanate    is   dis- 
solved out  with  hot  water  and  crystallized.     Ammonium 
sulphocyanate  is  easiest  made  by  warming  alcoholic  am- 
monia with  carbon  bisulphide, 

2NII3  -f  CS2  =  H2S  -f  NH4CNS. 

It  has  been  proposed  to  use  this  reaction  in  purifying 
coal  gas  from  CS2. 

The  sulphocyanates  of  Cu,  Pb,  Ag,  and  Hg  are  pro- 
duced by  mixing  salts  of  these  metals  with  either  of  the 
preceding.  Neutral  ferric  salts  give  no  precipitate  with 
them,  but  produce  an  intense  blood-red  color. 

Conversely,  these  reactions  serve  for  the  detection  of 
sulphur  and  of  prussic  acid. 

(I)  Sulphur,  by  heating  the  dried  substance  which  contains  it 
with  KCN;  extracting  the  sulphocyanate  formed  with  hot  water, 
filtering,  and  then  testing  with  a  dilute  solution  of  ferric  chloride. 
(2)  Prussic  acid,  by  exposing  to  its  vapors,  a  drop  of  silver  nitrate, 
white,  AgCN,  forms.  On  treating  this  with  a  small  quantity  of 
ammonium  sulphide,  black,  AgS,  and  soluble  ammonium  sulpho- 
cyanate, NH4CNS,  are  produced.  This  mixture  is  heated  gently  to 
expel  the  excess  of  NH4HS,  dissolved  in  water,  filtered,  and  tested 
with  ferric  chloride. 

Mercuric  sulphocyanate,  (CNS)2Hg,  has  the  curious  property 
of  enormously  increasing  in  volume  when  ignited.  It  is  used  in 
the  toy,  Pharaoh's  serpents. 

616.  The  oil  of  mustard  is  allyl  sulphocyanate, 

C3H5CNS. 


314  ORGANIC  CHEMISTRY. 

This  can  oe  made  by  decomposing  allyl  iodide.  C3II-I, 
by  an  alcobolic  solution  of  potassium  sulphocyanate.  A 
large  number  of  similar  compounds  have  boon  manu- 
factured which  are  known  collectively  as  the  "mustard 
oils." 

617.  Tests.  All  cyanogen  compounds  may  be  made  to 
yield  Prussian  blue.  This  may  be  effected  generally  by 
(1)  boiling  with  KI1O;  (2)  adding  a  crystal  of  efflor- 
esced FeSO4 ;  (3)  filtering  and  then  acidulating  with 
1IC1. 

Recapitulation. 

(1)  CX  is  a  negative,  univak-nt  radical,  with  three  isomeric  modi- 
fications.    Kach   isomer  lias  several   polymers. 

(2)  The    polymers   are  saturated;    as,  cyanogen  gas,  C2X2;   or  are 
radicals    having    a  valency  equal    to   the-   number  of    times   the 
CX  is  taken;   as,   (C3X3)"'. 

(3)  The  metallic  cyanides  contain  one  or  several    metals,  forming 
single  and  double  cyanitUs,  easily  decomposed,  poisonous  salts. 

(4)  CX  also  forms  complex  radicals;  as,  (CXO)',  (CXS)',  in  potas- 
sium cyanate  and  sulphocyanate,  and  with   XO2  as  (C5X5XO.j) 
in  the  nitro-prussides. 

(5)  C3X3  'forms    with   some   metals    aggregates   which   contain  the 
metals  in  both    the  "ous"  and  "ic"  states.     These  aggregates 
are  complex  radicals-,  like  the  ferro//,   ferric///  cyanogen. 

(0)  All  these  radicals  form  a  series  of  salts  with  the  metals  which 
are  derived  in  theory  from  an  acid.  Most  of  the  acids  are 
also  known. 


CHAPTER   XIX. 

THE    HYDROCARBONS. 

618.  The  hydrocarbons  comprise  a  number  of  isologous 
series  which  differ  by  1I2;  as,  the  paraffins,  CulI2,,f2  ; 
the  olefines,  CnII9n.  The  successive  numbers  of  each  of 
these  differ  by  CII2.  The  highest  number  known  con- 
tains C32,  and  we  may  expect  that  each  series  contains 
at  least  32  members,  but  in  no  case  have  all  the  suc- 
cessive terms  been  isolated. 

The  members  of  each  series  exhibit  properties  which 
are  strikingly  gradational.  The  lowest  members  of  each 
series,  CII4,  C3IIA,  02H2,  are  gases  at  ordinary  temper- 
atures. As  the  molecular  weight  increases  there  is  an 
almost  regular  increase  in  vapor  density  and  specific 
gravity,  in  boiling  and  in  melting  points.  Those  con- 
taining from  5  to  20  carbon  atoms  are  generally  liquids; 
the  highest  members  are  solids.  The  isomeric  modifica- 
tions are  very  numerous.  It  is  possible  to  construct  a 
normal  and  an  iso  series  for  the  paraffins,  olefines,  and 
acetylenes,  each  with  well  characterized  differences  and 
resemblances. 

All  these  hydrocarbons  are  capable  of  mixing  .perfectly 
together,  the  liquids  absorbing  the  gases,  dissolving  one 
another  and  the  solids.  Such  mixtures  of  hydrocarbons 
are  found  among  the  products  of  the  destructive  distilla- 
tion of  fatty  bodies  and  of  bituminous  coal.  Some  are 
found  native  in  petroleum,  in  Rangoon  tar,  etc. 

All  are  inflammable,  the  olefines  giving,  perhaps,  the 
brightest  flame.  Their  vapors,  mixed  with  air,  form 
dangerously  explosive  mixtures  ;  the  more  likely  to  be 

(315) 


316  ORGANIC  CHEMISTRY. 

produced   from   the    lowest  and   more   volatile   members. 
Serious   accidents   from   this   cause   are   of  very   common 


occurrence. 

619.  The  paraffins,  CMII2>M.2,  are,  for  the  most  part, 
inert  bodies,  capable,  however,  of  forming  substitution 
products  with  the  haloid  elements  ;  as, 

CtI4  +  Cl2  =  HCl-f  CH8C1. 

These  chlorides,  etc.,  heated  with  alkaline  hydrates,  yield 
the  corresponding  alcohols, 

cir3n+  Kiio-  KCI  +  cn3oii. 

They  are  obtained  artificially  from  alcoholic  haloidcs  by 
the  action  of  nascent  hydrogen,  CII8C1  +  H2==HC1  +  CI14. 

The  crude  petroleum  of  Pennsylvania  is  a  mixture  containing 
almost  the  "entire  series.  The  lighter  gases  readily  escape,  and  the 
remaining  liquid  is  subjected  to  a  process  of  fractional  distillation 
in  iron  retorts.  The  first  products  which  are  condensed  only  by 
freezing  mixtures,  are  called  cyinogene  and  rhigolene.  These  are 
used  only  for  producing  artificial  cold  by  their  rapid  evaporation. 
Next  in  order  are  liquids  boiling  below  100°C.  Such  as  gasoline 
(used  for  gas-  making),  naphtha  (used  for  paints  and  varnishes), 
and  benzene  or  light  oil  (used  for  illuminating  purposes  in  lamps 
without  wicks).  Then  follow  the  ordinary  coal-oils.  ;'  Paraffin," 
a  thicker  oil,  used  for  lubricating;  a  very  soft  paraffin,  "vaseline," 
used  for  pomades,  etc.;  a  pliable  paraffin,  used  for  chewing  gum; 
and  the  hard  paraffin,  melting  about  40°C,  used  for.  candles.  A  res- 
idue of  porous  coke  is  left.  All  these  substances  are  mixtures,  the 
names  given  to  them  do  not  express  constant  composition.  They 
are  afterwards  rectified  by  agitation  with  sulphuric  acid  (from  2^> 
to  40^),  which  removes  the  olefines  and  some  of  the  color,  washed 
with  water  and  with  caustic  soda  to  remove  the  last  traces  of  acid. 
They  are  then  ready  for  market. 

Those  "kerosines,"  which  are  sold  for  illuminating  purposes,  are 
graded  by  "  the  flashing  test."  This  is  variously  defined  by  State 
laws,  but  usually  means  the  temperature  at  which  the  vapors  of 
the  oil  escape  with  sufficient  rapidity  to  enkindle  when  a  very 
small  flame  is  held  i  of  an  inch  above  the  surface  of  the  liquid. 
Ohio  test,  110°F  =  43°C.  It  is  approximately,  20°C  or  35°F,  below 


THE  HYDROCARBONS.  317 

the  "fire  test,"  which  is  the  temperature   at  which   the  oil  burns. 
Of  course  the  boiling  point  is  much  above  either  of  these. 

The  "kerosines"  are  those  paraffins  that  are  distilled  between 
150°  and  300°C.  If  properly  manufactured,  such  oils  are  perfectly 
safe  for  household  illumination.  Unfortunately,  at  high  tempera- 
tures, the  complex  paraffins  have  a  tendency  to  "  crack ;"  that  is, 
to  split  up  into  several  lower  paraffins  and  olefines,  so  that  even 
the  heavy  oils  often  contain  a  large  amount  of  the  lighter  oils.  It 
is  also  customary  to  prepare  illuminating  oils  by  mixing  benzene 
with  heavier  products.  These  volatile  products  easily  escape,  and 
produce  explosive  mixtures  with  the  air  in  the  lamps.  No  oil  is 
safe  that  flashes  when  a  lighted  match  is  held  near  it. 

620.  Methane,  CH4,  also  called  marsh  gas,  from  the 
fact  that  it  may  be  obtained  from  stagnant  marshy  pools, 
is   found   in   coal    mines   as    "fire-damp,"  in  the  springs 
of  inflammable  gas  common  on  the  borders  of  Ohio  and 
Pennsylvania,  and   forms  about  80  per  cent  of  ordinary 
coal  gas.     It  is  artificially  prepared  by  heating  an  inti- 
mate  mixture   of  dried  sodium   acetate  with   double  its 
weight  of  soda-lime, 

CH3COONa  +  NaIIO:=CH4  +  Na2CO8. 

Methane  is  a  colorless,  inodorous  gas,  about  half  as 
heavy  as  air,  vapor  density—  l-^--.=  S.  It  burns  with  a 
yellowish  flame.  CH4  +  O4  =  CO2  +  2H2O,  but  when 
mixed  with  double  its  volume  of  oxygen,  it  enkindles 
with  explosive  violence. 

Ethane,  C2H6  ;  propane,  C3H8 ;  butane,  C4H10,  gases 
at  ordinary  temperatures,  are  found  mixed  with  methane 
in  the  gases  which  escape  in  boring  for  petroleum.  These 
wells  have  been  used  extensively  for  lighting  villas  and 
villages,  for  fuel  in  stoves  and  furnaces,  and  more  re- 
cently for  the  manufacture  of  lampblack. 

621.  The  olefines,  CHH2n,  afford  an  excellent  example  of 
a  series  of  polymers,  being   all   multiples   of  CH2,  me- 
thene.      About  20  olefines  are  known,  which,  so  far  as 
they   exist   in    the   free   state,  are    saturated    compounds 


318  ORGANIC  CHEMISTRY. 

capable  of  forming  substitution  compounds  with  chlor- 
ine, etc.;  as,  C2H3Cl  =  chlorethene. 

The  olefines  also  act  as  dyad  radicals,  directly  uniting 
with  the  halogens  and  with  concentrated  sulphuric  acid; 
as,  CII2:CH2  +  C12  =  C1I2C1-CH2CI  or  C2II4C12,  a 
pair  of  the  '-latent  carbon  bonds"  opening  for  the  C12. 
They  tend  also  to  form  polymers.  For  example:  two 
molecules  of  amylene,  C5II10,  condense  to  one  of  decene, 
C,,H20. 

The  only  important  olefine  is  cthylene,  C2H4.  It  is 
prepared  by  heating  alcohol  with  G  times  its  weight  of 
strong  sulphuric  acid,  C2H5OII— II2O^c7lI4.  (P.  323.) 
It  was  called  olefiant  gas,  because  it  forms  with  01 2,  an 
oily  liquid,  which  is  a  diatomic  haloid  ether.  (P.  395.) 

Ethylene  is  a  colorless,  poisonous  gas,  condensable  by 
pressure  to  a  liquid  which  boils  at  — 110°.  Its  vapor 
burns  with  a  brilliant  white  flame.  It  and  its  homo- 
logues  constitute  the  " illuminants"  in  ordinary  coal  gas, 
of  which  they  form  from  5%  to  10^. 

Propylene,  03H6,  and  butylene,  04H8,  are  also  gases 
at  ordinary  temperatures.  There  are  3  butylcnes  and  4 
amylenes  known.  The  latter  are  liquids  with  boiling 
points  between  25°0  and  75°C. 

622.  The  normal  acetylenes  (CnII2n_2)  form  crystalline 
precipitates  when  their  vapors  are  passed  into  an  am- 
moniacal  solution  of  cuprous  chloride.  This  precipitate 
treated  with  HC1  yields  the  acetylene  hydrocarbon  in 
the  pure  state.  It  contains  the  trivalent,  CH,  as  in  the 
normal  allylene,  CIl£E:C-CH3.  The  isomers  do  not  form 
the  cuprous  compound,  and  contain  different  radicals ; 
as,  allene,  CH2^C  =  CH2. 

Acetylene,  C2H2,  or  CH^CH,  is  a  colorless  gas,  of  an 
unpleasant  odor,  which  burns  with  a  bright,  but  smoky, 
flame.  It  is  a  common  product  of  the  incomplete  com- 
bustion of  organic  bodies. 


THE  HYDROCARBONS.  319 

It  is  easiest  obtained  by  causing  the  gas  in  a  Bunsen's  burner 
to  burn  at  the  bottom  of  the  tube.  The  products  of  the  combus- 
tion are  drawn  by  means  of  an  aspirator  through  an  ammonincal 
solution  of  cuprous  chloride.  A  red  precipitate  of  di-acetylene  — 
cuprous  oxide  —  forms: 


2C2H2-f  2Cu/2Cl2  +  H2O-=4IICl-f  CII^C    Cu2    O    Cu2-  C=CH, 

which  is  explosive  when  dry.     This  precipitate,  treated  with  hydro- 
chloric acid,  yields  pure  acetylene: 

C4H2Cu4O  -f  4IIC1  =  2Cu2Cl2  +  II2O-f  ^\l~2. 

The  chief  interest  which  attaches  to  acetylene  arises  from  the  fact 
that  it  is  the  only  hydrocarbon  which  lias  been  produced  by  direct 
union  of  its  elements,  and  that  from  it  may  be  derived,  with  greater 
or  less  trouble,  an  enormous  number  of  carbon  compounds. 

623.  Few  hydrocarbons  of  the  higher  series  have  been 
isolated.  The  tcrpenes  have  the  general  formula,  CnII2n_4; 
as,  turpentine,  C10H16,  but  they  belong  to  the  aro- 
matic group.  The  general  formula,  CnH2n_6,  includes  two 
different  bodies,  di  propargyl,  IIC  =  C-CII2-CH2-C  =  CH, 
constructed  as  an  "open  chain,  "-and  benzene,  C6H6,  the 
first  of  the  hydrocarbon  series  with  closed  chains,  which 
will  be  considered  among  the  aromatic  compounds. 


Recapitulation. 

(1)  The    hydrocarbons   all   act   as   saturated    bodies,  containing  an 
even  number  of  hydrogen  atoms. 

(2)  Such    hydrocarbons    as   contain    an    odd    number    of    hydrogen 
atoms  are  perissad  radicals.     So,  also,  many  are  known   which 
act  as  artiad  radicals. 

(3)  They  may  be  arranged  in    homologous  series,  whose  members 
differ  successively  by  CH2. 

(4)  Also,  in  isologous  series,  differing  by  H2. 

(5)  They  may  be  obtained  by  synthesis,  but  their  chief  sources  are 
the  natural  oil  wells  and  bituminous  coal. 

(6)  They  are  employed  (1)  as  refrigerants,  (2)  as  illuminants,  (3)  as 
lubricants. 

(7)  The  chief  series  are  the  paraffins,  the  olefines,  and  the  benzenes. 


CHAPTER    XX. 

THE    ALCOHOLS. 

624.  All  alcohols  contain  hydroxyl,  and  arc  defined  to 
be  hydroxides  of  hydrocarbon  radicals;  as,  ethyl  hydrox- 
idc,  ('oIljOH.     They  may  be  regarded   as  formed   from 
saturated  hydrocarbons  by  the  substitution  of  hydroxyl 
for  hydrogen.     Thus,  from  propane,  C3H8,  are  derived, 
C8II7OII,  propyl  alcohol;  C3II6(OII)2,  propone  alcohol; 
C3II5(OII)3,  propenyl  alcohol. 

Alcohols  are  classed,  according  to  the  number  of  hy- 
droxyl groups  they  contain,  into  monohydric  (Oil),  di- 
hydric  (OII)2,  triliydric  (OII)3,  etc.  It  is  proposed  to 
use  the  termination  ol  for  all  these;  as,  monohydric  — 
alcohols;  dihydric  =  glycols;  trihydric  =  glyccrols  and 
pyrogallols ;  hexhydric=mannitolS)  etc. 

625.  The   monohydric  alcohols   include   several    series 
built    up    upon    monovalent   radicals;    as,    (1)    from   the 
paraffins,  the   methyl  alcohols,  or   carbinols,  OnII2B+,O,  or 

;  (2)  from  the  olefines,  the  vinyl  alcohols, 
,  and  others  of  the  "open  chain"  sort.  (3) 
The  "closed  chain''  benzenes  give  rise  to  the  benzyl  al- 
cohols,* CnII2(1_7CII2OH,  and  their  isomers,  the  phenols, 
CMH8|_7OH,  (+CH2). 

The  polyhydric  alcohols  also  contain  different  series, 
but  these  are  not  so  well  known,  nor  so  distinctly  classi- 
fied as  the  monohydric.  These  alcohols  increase  gradu- 
ally in  sweetness  until  the  hexhydric  alcohols  are  readied. 

*  These  should  be  called  the  benzoles.  Unfortunately  the  words  benzole 
and  benzene  are  applied  both  to  the  lighter  paraffins,  CnH2n+2,  and  to  the 
first  of  the  aromatic  hydrocarbons,  C6H6. 


ALCOHOLS. 


321 


The  mannitols,  CnH2n_4(OH)6,  are  natural  alcoholic 
sugars;  as,  mannite. 

The  other  sugars  are  related  to  these  ;  but  in  what 
way  has  not  been  satisfactorily  ascertained. 

626.  The  carbinols,  or  the  methylic  series  of  alcohols, 
have  been  more  thoroughly  investigated  than  the  others. 
The  following  table  exhibits  the  best  known  members  of 
the  series. 


o  * 

o  • 

o  ' 

o 

o 

o 

O 

0 

O    O 

O 

t-5 

*• 

00 

•» 

g  • 

2L 

sr 

co 

i; 

I  • 

! 

| 

9 
1 

| 

w 

7  S 

o     y 
^    ^ 

1 

Z3 

OS 

o 

p  . 

p     . 

o 

— 

n' 

n 

p 

g:   p 

— 

a  > 

0  » 

S* 

r  < 

p 

Q    • 
3 

SS 

Spermaceti 

o 

o 
•z. 

\ 

I 

Castor-oil. 

9 

-r 

I 

i—  n 

r 

;  Ferinentati 

Ferraentati 
i  Fusel-oil.  . 

O 

00* 

S- 
o" 

0 
O 

^ 

o 

o 

•J 

? 

B 
i 

3 

3 

O 

6 

CP5 

0 

CD 

< 

o 

C! 

~ 

n 

£ 

o 

8 

• 

• 

erine. 

•     ? 

O    ' 

» 
o 

O    ' 

to 

P    ' 

o 

00 

~. 

O 

A 

0 

P 

o  o 

CO           tO 

O 

X5 

a  • 

01 

ja  • 

a  • 

a 

a 

~ 

a 

a 

a  ^a 

C? 

^ 

a  ' 

o  • 

§ 

o 

r: 

5 

C 

a 

o 

o  o 

a  a 

O 

a 

p 

Oi     S 

s 

^~I 

«g 

^; 
-  1 

Oi 

^J      GO 

S 

.  o 

.  o 

.  *"*       ^* 

o 

o 

0 

o 

o 

O         O 

o 

IT!  O 

05 

pi 

(i 

O 

i£t      — 

^ 

O  ^ 

i 

^i 

3 

• 

•    • 

• 

O 

0 

o 

O 

0 

O     0 

O 

...OQ 

QO 

C^ 

cc 

GO 

GO     -^7 

H  F 

o 

55 

-a 

-u 

O5     4^ 

GO 

C^O 

Chem.— 21. 


322  ORGANIC  CHEMISTRY. 

627.  The  higher  members  have  numerous  isomers  which 
are  classified  as  primary,  containing  (CH2OH)' ;  second- 
ary, containing  (CIIOH)";  and  tertiary  alcohols,  contain- 
ing   (COII)'".      These    groups    behave    differently    upon 
oxidation,  and  are,   therefore,   metamers.      The   primary 
have  lower  boiling  points  than  the  secondary,  and  these 
than   the   tertiary.      The   normal   alcohols   are   of  higher 
boiling  points  than  their  "iso"  forms,  etc. 

Some  of  these  alcohols  exist  free  in  nature,  especially 
in  plants  of  the  parsnep  family.  Others  are  obtained  by 
saponifying  the  natural  ethers,  like  the  oil  of  winter- 
green;  and  some  are  obtained  by  synthetical  operations. 
The  process  of  fermentation,  which  is  employed  in  mak- 
ing ordinary  alcohol,  not  unfrequently  yields  also  several 
alcohols.  "Fusel-oil"  is  a  mixture  of  the  lower  carbon 
alcohols,  from  propylic  to  caprylic. 

628.  All  the  anhydrous  alcohols  dissolve  potassium  and 
sodium  with   the  formation  of  solid  compounds  called  al- 
coholatcs;  as,  C2H5OK  =  potassium  ethylate.     These  bod- 
ies   readily   exchange    their   metals    for    other   equivalent 
radicals;  as,  C2II5OXa-f (12II5Cl=NaCl-f C2H5-O-C2H6 
r=  ethyl  ether. 

629.  The  alcohols  act  as  weak  compounds,  readily  com- 
bining with   the  acids,  setting  free  a  molecule  of  water, 
and  forming  the  so-called  "compound  ethers;"  e.  g., 

CII3OH  +  HONO  =  II20+CH,  O  •  NO  =  nitrous  ether. 

With  polybasic  acids,  intermediate  compounds  may  be 
also  formed;  thus,  from  ethylic  alcohol  and  sulphuric 
acid  may  result: 

(1)  C2H5OH  +  HO    S02    OH  =  H2O  +  C2H5O    SO2    OH,  acid 
ethyl  sulphate. 

(2)  (C2H5OH)2+  HO    SO2-  OH  =  2H2O+C2H5O-  SO2    C2H50, 
ethyl  sulphate.     Both  of  these  are  produced  in  the  manufacture 


THE  ALCOHOLS.  323 

of  "sulphuric  ether"  at  temperatures  below  154°C.     Above  this 
temperature  results  from  the  foregoing,  either: 

(3)  C2H5OH    SO2    OH  -f  C2H5OH  =  (HO)2SO2  +  (C2H5)2O  = 
the  common  ether;  or, 

(4)  C2H5O  •  SO2  •  C2H5O  heated  strongly  =  (HO)  2SO2  -f  2C2H4  = 
ethylene.     It   is   to   be  noted   that  in  both  cases  the  sulphuric 
acid  is  regenerated. 

630.  Methyl  alcohol,  CH3OH,  may  be  obtained  from 
the  oil  of  wintergreen,  CH8-O  •  C7H5O2  =  methyl  salicy- 
late,  and  from  crude  wood  vinegar.      Wood-vinegar,  ob- 
tained by  the  destructive  distillation  of  wood  (Exp.  162), 
contains   about    one   per   cent    of  methyl    alcohol.      The 
crude    wood-spirit   has  an  offensive  odor  and   taste,  but 
pure  methyl  alcohol  is  a  limpid,  volatile  fluid,  very  sim- 
ilar in  odor  and  taste  to  ethyl  alcohol. 

It  has  also  many  of  the  properties  of  ethyl  alcohol, 
and  is  used  in  the  arts  for  making  varnishes  and  dis- 
solving volatile  oils,  and  in  lamps  as  a  convenient  source 
of  heat.  In  England,  a  mixture  of  ordinary  alcohol 
with  ten  per  cent  of  methyl  alcohol  is  sold,  free  of  ex- 
cise duty,  under  the  name  of  methylated  alcohol,  for 
manufacturing  purposes. 

631.  Ethyl    alcohol,    C2H5  OH   or    CH3CH2OH,    has 
been    prepared   synthetically,   but   the    process   is    time- 
consuming.     It  is  present  in  all  fermented  and  distilled 
liquors,  and  gives  to  them  their  intoxicating  properties. 
Absolute  alcohol  is  a  colorless,  limpid,  easily  inflammable 
liquid,  of  fiery,  pungent  taste,  and  pleasant  odor.     Sp.  gr. 
0.79;   boiling   point,    78°.4C.    (173°F).      It   has   recently 
been  solidified  by  cold  of — 131  °C.     It  is  sometimes  used 
for  filling  thermometers  intended  for  measuring  low  tem- 
peratures. 

Absolute  alcohol  dissolves  potassium  and  sodium,  forming  ethy- 
lates,  like  C2H5  •  OK.  With  chlorine  it  forms  a  variety  of  prod- 
ucts:  (1)  CH3CH2OH  +  Cl2-=2HCl  +  OH3CHO=aWeMe,  which  is 
the  principal  product  when  weak  alcohol  is  used. 


324  ORGANIC  CHEMISTRY. 


(2)  CH3CH2OH-|-a8  =  5Ha-f  CCl3-CHO  =  cWora/,  which  is  a 
product  of  long-continued  action. 

(3)  And    also    acts    oxidi/.ing    when    in    presence    of    water;    as, 
CH3CH2OII    t   II2O  r  C14  =  4HC1  +  CII3C<>OII  —acetic  acid.     Still 
further,  the  nascent  hydrochloric  and  acetic  acids,  liberated  by  these 
reactions,  produce,   with  other  alcohol   molecules, 

(4)  C2II6OH-f  IICl  =  H2O-f  C,II5C1   --ethyl  chlnridr  ;  and, 

(5)  C2II,,OII  t  C2II402^II20  +  C2IL,    O     C2ll3l)---=  ethyl  axtate. 

((>)  Aldehyde  and  acetic  acid  are  also  produced  by  the  oxidation 
of  alcohol;  as,  by  chromic  mixture,  etc. 

(7)  When  caustic  potash  is  present  the  chloral,  formed  by  re- 
action ('2),  is  converted  to  potassium  formate  and  dWorq/brm, 

CCI,    CIIO  -f  KHO^  II,  COOK  -f  CIIC13  =chloroform. 

Iodine,  under  like  conditions,  produces  iinlofifrm,  CIII3,  which  i.H 
obtainable  upon  evaporation  in  yellow  scales,  and  is  a  valuable 
test  for  the  presence  of  alcohol. 

Alcohol  dissolves  many  inorganic  substances  ;  as,  I, 
KIK),  SrOlo,  but  is  especially  useful  as  a  solvent  for 
organic  compounds,  like  the  alkaloids,  essential  oils,  and 
the  resins;  e.  g.,  camphor.  It  mixes  with  water  in  all 
proportions,  causing  an  elevation  in  temperature,  and  a 
contraction  in  volume  —  51.9  vols.  of  alcohol  -f-  48.1  vols. 
of  water  contracting  to  9G.5  volumes,  producing  a  mix- 
ture which  is  very  nearly  C2H5'OH,  3II2O.  Accord- 
ingly, it  readily  absorbs  water  from  other  substances, 
coagulating  albumin  almost  instantaneously,  and  hence 
acting  as  an  active  poison  ;  but  like  several  other  poisons 
also  acting  as  a  preservative  for  animal  tissues  immersed 
in  it. 

632.  Decay  and  fermentation  are  natural  processes 
which  result  in  the  breaking  up  of  complex  organic  sub- 
stances into  simple  compounds.  It  is  generally  custom- 
ary to  apply  the  term  "decay"  to  the  putrefaction  or 
rotting  of  substances  containing  nitrogen,  as  albumin. 
This  takes  place  rapidly  in  warm,  moist  air,  and  ap- 


THE  ALCOHOLS.  325 

parently  spontaneously,  producing  carbonic  anhydride, 
ammonia,  water,  and  a  variety  of  offensively  smelling 
products  which  have  never  been  utilized. 

Fermentation  is  applied  to  the  decompositions  of  non- 
nitrogenous  bodies,  yielding  of  themselves  no  offensive 
odors,  but  producing,  besides  carbonic  anhydride  and 
water,  useful  products  like  alcohol  and  acetic  acid.  There 
are  several  kinds  of  fermentation  which  have  been  named 
saccharine,  vinous,  acetic,  lactic,  etc.,  after  the  useful 
product.  Decay  and  fermentation  are  supposed  to  be 
due  to  the  presence  of  a  third  body,  called  a  ferment. 

Ferments,  so  far  as  known,  always  contain  nitrogen. 
They  are  of  two  kinds:  (1)  Unorganized  soluble  bodies, 
which  are  undergoing  some  sort  of  a  change,  as  the 
ptyalin  of  the  saliva  and  the  diastase  of  grain.  (2)  Or- 
ganized structures,  which  are  plants  or  animals  actually 
living  and  growing,  like  the  yeast-plant. 

633.  Two  theories  of  fermentation  emphasize  one  or  the 
other  of  these  facts.     LIEBIG  believed  that  when  nitrogen- 
ous  bodies   decay,  a  tremendous   disturbance   is   set   up 
among   their   molecules,   which    is    capable    of  inducing 
similar  disturbances   among  the   molecules   of  carbohy- 
drates, like  starch.     The  molecular  change  which  thereby 
results  is  fermentation  ;  the  decaying  body  is  a  ferment, 
and  is  said  to  act  by  its  presence  (catalysis). 

PASTEUR  supposed  (1)  that  everywhere  in  the  atmos- 
phere are  "germs"  of  organized  bodies  as  abundant  as 
the  motes  in  the  sunbeam;  (2)  that  when  these  germs 
fall  into  a  nidus  containing  their  proper  food,  air,  mois- 
ture, and  a  suitable  warmth,  they  grow;  (3)  by  their 
growth  nitrogenous  substances  pass  into  decay;  non- 
nitrogenous  substances  into  some  sort  of  fermentation; 
(4)  and  that  each  kind  of  fermentation  is  excited  most 
readily  by  some  "peculiar  microscopic  plant  or  animal. 

634.  The  ferment    in   vinous    fermentation    is    usually 


326 


ORGANIC  CHEMISTRY. 


yeast.  Yeast  is  a  monocellular  plant  which  grows  at  the 
expense  of  the  nitrogenous  matters  which  are  present  in 
the  crude  fruit  juices  and  malt  infusions.  The  best  con- 
ditions for  its  growth  are  aqueous  solutions  containing 

less  than  20^  of  sugar, 
and  a  temperature  be- 
tween 25°  and  35°C.  It 
grows  with  great  rapid- 
ity, often  increasing  in 
weight  seven  fold  in  as 
many  days.  It  may  be 
killed  by  freezing  or  by 
boiling,  and  by  the  pres- 
ence of  antiseptics.  Nev- 
ertheless, it  may  be  dried 
by  pressure,  and  is  an 

FIG.  102.    YEAST-PLANT.  artielc  of  «>mmerco. 

When  examined  by  the  microscope,  two  sets  of  cells  are  always 
found,  which  has  led  some  to  suppose  that  there  are  really  two 
yeast-plants.  One  of  large  cells  (saccharomyces  cerevisiee),  which 
is  the  top  yeast,  used  in  brewing  ale  and  in  the  mash  of  "high 
wines;"  the  other  much  smaller  (penicillium  glaucum),  of  compar- 
atively slow  growth,  which  is  the  "bottom  yeast"  of  lager  beer. 
This  bottom  yeast  is  supposed  also  to  be  an  active  ferment  in 
butyric  and  lactic  acid  fermentation. 

635.  The  glucoses,  C6II12O6,  are  the  only  substances 
which  may  be  made  to  undergo  vinous  fermentation. 
They  exist  in  most  ripe  fruits,  and  are  easily  obtained 
from  cane  sugar,  or  from  starch  by  assimilation  of  wa- 
ter; cane  sugar,  Cl  21l22^i ,  -f  H2O^=2C6H1  2O6  ; 

starch,  C6H1006+H20  =  C6H12Oe;  glucose. 


The  chief  products  of  vinous  fermentation  are  carbonic  anhy- 
dride and  ethylic  alcohol,  C6H12O6  ==  2CO~7  +  2C2H5OH,  mixed 
always  with  small  amounts  of  glycerol  and  of  succinic  acid;  fre- 
quently, also,  traces  of  acetic  and  lactic  acids,  and  the  higher 


THE  ALCOHOLS.  327 

homologues,  propylic,  butylic,  and  amylic  alcohols,  which  are  sep- 
arated in  distillation  as  "fusel -oil."  It  will  also  be  remembered 
that  wine  and  other  fermented  liquors  contain  the  sugar  which  has 
escaped  fermentation  and  soluble  matters,  like  tartaric  or  citric 
acids  derived  from  the  fruit  juices,  or  from  the  malt  extract. 

636.  Fermented   liquors,  such   as  wine  and   cider,  are- 
made   from   the    natural    fermentation    of  the    expressed 
juice  or  must  of  grapes  and  apples.     On  exposure  of  the 
juice  to  the   air,  the   albuminous   matters  present  enter 
into  the  state  of  decay,  and  a  spontaneous  fermentation 
is  set  up  in  the  fruit  sugar.     No  yeast  is  added.     When 
the  fermentation  ceases,  the  clear  wine  is  drawn  off  into 
casks  and  set  in  cool  cellars  to  ripen.     As  the  wine  be- 
comes stronger  in  alcohol,  a  red  crust,  called  argol,  which 
is  acid  potassium  tartrate,  separates  out,  and  the  wine 
becomes  sweeter.     The  malic  and  citric  acids  present  in 
cider  and  currant  juice  can  not  be  so  withdrawn.     The 
bouquet,  or  flavor,  of  these  liquors  is  due  to  small  quan- 
tities of  ethers,  like  the  acetic  and  oenanthylic. 

Strong  wines,  like  sherry,  which  do  not  change  to 
vinegar  upon  exposure  to  the  air,  contain  from  15  to  20 
per  cent  of  alcohol.  The  sour  wines,  like  claret  and  the 
Ehine  wines,  contain  from  7  to  12  per  cent  of  alcohol, 
and  almost  no  sugar.  In  sparkling  wines,  like  cham- 
pagne, a  part  of  the  sugar  ferments  after  the  wine  is 
bottled,  thereby  evolving  CO2. 

637.  Ale  and  beer  are  fermented  liquors  prepared  from 
malted    barley.      The    operation    of  malting    consists    in 
causing  moistened   barley  to  germinate   in  warm,  moist 
air,  for  10  or  15  days.     The  germ  is  then  killed  by  dry- 
ing.    It  is  now  malt,  and  contains  most  of  the  starch  of 
the  barley,  some  dextrine  and  sugar,  and   a  remarkable 
nitrogenous    substance    called    diastase,   directly   derived 
from  the  germ  of  the  plant.     This  diastase  is  a  soluble 
ferment,  capable  of  converting  1000  times  its  weight  of 
starch  into  glucose,  C6H10O5  -}-  H^O  —  C6H1206,  or  ^en 


328  ORGANIC  CHEMISTRY. 

times  the  weight  of  the  Starch  associated  with  it  in  the 
malt.* 

In  brewing,  the  malt  is  first  screened  and  crushed.  It 
is  then  mashed  in  large  tubs  with  water,  and  heated  for 
several  hours  at  75°C.  In  this  time,  the  diastase  con- 
verts nearly  all  of  the  starch  of  the  grain  into  dextrine 
and  malt  sugar,  which  dissolve.  The  clear  liquor  strained 
from  the  spent  barley  husks  is  the  wort.  It  has  a  sweet, 
insipid  taste. 

The  wort  is  now  boiled  in  large  copper  kettles,  and  a 
quantity  of  hops  added.  The  hops  give  a  bitter,  aro- 
matic taste  to  the  beer,  and  perhaps  act  as  a  narcotic. 
By  the  boiling,  the  diastase  is  destroyed,  the  albuminous 
matters  coagulated,  and  the  wort  becomes  clarified.  The 
clear  liquor  is  now  drawn  oil',  cooled  rapidly,  and  trans- 
ferred to  enormous  tubs  called  the  fermenting  vats. 

At  this  stage,  brewers  of  ale  and  of  lager  beer  vary  in 
their  methods.  Stock  ale  contains  more  alcohol,  and  re- 
quires a  stronger  malt  than  lager  beer;  and  ale  is  made 
from  top  yeast;  lager,  from  bottom  yeast. 

The  yeast  which  is  now  added  sets  up  a  vinous  fer- 
mentation. The  process  continues  for  several  days  (3  to 
8),  or  until  nearly  three  fourths  of  the  glucose  has  been 
converted  to  alcohol  and  carbonic  anhydride, 

yeast +  C6H1206  =  2C02+2C2H5OH. 

The  clear  liquor  is  now  separated  from  the  yeast;  the  ale 
is  drawn  into  casks,  and  the  lager  into  enormous  tuns, 
which  are  placed  in  cool,  quiet  cellars.  In  both,  a  slow 
fermentation  continues  for  some  time,  consuming  sugar, 
but  rendering  the  beer  stronger,  besides  charging  it  with 
the  froth -producing  carbonic  anhydride.  In  a  few  days 
the  ale  casks  are  closed  by  bungs,  but  it  requires  several 


*  Distillers  and  some  brewers  take  advantage  of  this  property,  adding  to 
the  barley  mash  large  quantities  of  other  raw  grain,  rice,  or  glucose. 


THE  ALCOHOLS.  329 

months  before  the  lager  is  fit  to  be  transferred  to  the 
kegs  in  which  it  is  sold.  The  color  of  ale  and  beer  is 
due  to  caramel,  which  is  produced  when  malt  is  roasted. 
Lager  beer  contains  from  one  to  five  per  cent  of  alco- 
hol; the  strong  ales,  as  high  as  ten  per  cent.  These 
beverages  also  contain  a  little  unchanged  sugar,  dex- 
trine, albumin,  an  extract  from  the  hops,  besides  traces 
of  acetic,  lactic,  and  succinic  acids. 

638.  Distilled  liquors  are  first  fermented  and  then  dis- 
tilled; as  brandy  is  distilled  from  wine.  Most  ardent 
spirits  are  made  by  first  malting  and  mashing  barley, 
as  in  the  process  of  making  ale.  The  diastase  of  the 
malt  is  employed  to  convert  as  large  a  quantity  as  pos- 
sible of  rye,  corn,  rice,  crushed  potatoes,  etc.,  into  glu- 
cose. No  hops  are  added,  nor  is  the  wort  boiled.  A 
large  amount  of  yeast  is  then  added,  and  the  fermenta- 
tion made  as  complete  as  possible  to  convert  all  the 
sugar  into  alcohol.  The  "sweet  mash,"  prescribed  by 
excise  law,  is  completed  in  48  hours;  the  "sour  mash" 
requires  a  longer  time,  also  setting  up  an  acid  fermenta- 
tion by  which  alcohol  is  lost,  but  which  is  thought  to 
improve  the  flavor  of  whiskey. 

The  fermented  mixture  is  now  brought  into  stills,  and 
subjected  to  fractional  distillation.  The  first  product  is 
thrown  back  into  the  still,  the  next  is  "high  wine," 
containing  from  40  to  70  per  cent  of  alcohol,  and  then  a 
weaker  "  low  wine,"  which  is  reserved  for  redistillation. 

Proof-spirit  is  a  mixture  of  49|  parts  of  alcohol  with  50^  parts 
of  water.  The  high  wines  are  either  rectified  into  cologne  spirit 
and  whiskeys  by  filtering  through  animal  charcoal,  which  absorbs 
both  the  fusel -oil  and  coloring  matters,  or  they  are  redistilled  into 
commercial  alcohol,  containing  as  high  as  92^>  alcohol. 

The  strongest  commercial  alcohol,  98^,  is  treated  also  with 
quick  lime,  which  combines  with  the  water,  and  is  then  again  dis- 
tilled. Absolute  alcohol,  100^,  is  made  by  repeating  this  process. 
It  should  not  give  a  blue  tinge  to  anhydrous  cupric  sulphate. 


330  ORGANIC   CHEMISTRY. 

639.  As  regards  spirituous  liquors,   it  may  be  added 
that   gin    owes    its    flavor    to  juniper    berries.      Rum    is 
made    from    molasses,    arrack    from    rice,    koumiss    from 
milk.     The  cordials   contain    cologne  spirits,  various  es- 
sential oils,  and  sugar. 

Most  ardent  spirits,  when  first  distilled,  have  a  raw,  fiery  taste, 
which  becomes  milder  when  they  are  kept  for  some  time  in  wooden 
barrels.  A  portion  of  the  spirit  escapes,  and  with  it  much  of  the 
bye  products,  as  aldehyde,  fusel-oil,  etc.,  which  are  replaced  by  a 
characteristic  flavor  or  bouquet.  This  bouquet  is  supposed  to  be 
due  to  the  oxidation  of  the  higher  alcohols  present,  and  the  conse- 
quent formation  of  fragrant  fruit  ethers.  "Ckmipounders  of  liquors," 
by  the  aid  of  ethers  made  from  the  various  fusel-oils,  have  been 
able  to  make  from  cologne  spirits  any  kind  of  whiskey,  brandy, 
gin,  etc.,  so  excellently  well  as  to  deceive  the  best  judges.  §758. 

640.  The  term  "fusel-oil"  is  given  to  a  variable  mix- 
ture of  several  alcohols  of  high  boiling  point,  which  pass 
over  at  the  end  of  an  ordinary  distillation  of  "  spirits." 
Potato  fusel   is  mainly  iso-amyl  alcohol.     Beet-root  fusel 
is    iso-butyl    and    iso-amyl    alcohol.      Apple-brandy   fusel 
is   propyl  alcohol.     The   fermented    marc  of  grapes  con- 
tains in  its  fusel,  propyl,  hexyl,  and  octyl  alcohols,  sep- 
arable by  a  careful  fractional  distillation. 

641.  Iso-amyl    alcohol,    which    is   the    ordinary   amyl 
alcohol    of  fermentation,  requires   further   mention.     Es- 
pecially,  because    it   is   a    mixture   of  two    isomers,  one 
optically  inactive,  the  other  with  a  right-handed   polar- 
ization.     It    does    not   mix   with    water,   and   is   a   good 
solvent  of  many  alkaloids,  like  morphine;    hence  it  has 
been  applied  to  remove  these  bodies  from  aqueous  mix- 
tures that  contain  them. 

642.  Cetyl  alcohol,  C16H33OH,  is  a  solid,  white,  taste- 
less mass,  which  is  obtained  by  saponifying  the  sperma- 
ceti found  in  sperm  whales. 

C16H33-O  •  C16H31O  =  cetyl  palmitate. 


THE  ALCOHOLS.  331 

Ceryl  alcohol  is  produced  from  Chinese-wax;  and  myricyl 
alcohol,  from  that  part  of  common  bees-wax  which  is 
insoluble  in  ethyl  alcohol. 

643.  Allyl   alcohol,    C3H5OH  =  C2H3CH2OH,  is   the 
only  well    known    alcohol   of  its   series.      It   is  obtained 
from  glycerin,  which    is   propenyl   alcohol,  C3H5(OH)3, 
by  heating  this  with   one  fourth  of  its  weight  of  oxalic 
acid.     It  resembles  ethyl  alcohol;   sp.  gr.,  0.8G;   boils  at 
97°C.     It  yields  on  oxidation   acrolein,  C2H3- CHO,  an 
aldehyde,    and    C2H3-COOH,    acrylic    acid,    but    mostly 
formic  and  acetic  acids.     It  is  especially  interesting  be- 
cause of  its  compounds  with  sulphur,  which  exist  natur- 
ally in  alliaceous  plants  and  some  cruciferae,  and  which 
have   also    been   produced    artificially,   as    oil    of  garlic, 
(C3H5)2S,    a    true    sulpho-ether,    and    oil    of    mustard, 
C3H5  •  S  •  ON,   a   sulpho    cyanate.     Propargylic   alcohol, 
C3H3OH,  of  the  series  CnH2n_3OH,  is  also  known.     The 
other  monatomic  alcohols  belong  to  the  benzene  and  cin- 
namine  series. 

644.  The  glycols  are  dihydric  alcohols  of  the  general 
formula,     CnH2n(OH)2.       They     may     contain     primary 
(CH2OH),   secondary  (CHOH),  or   tertiary  (COH),  al- 
cohol groups;    e.  g.,  ethene  glycol  is  a  double  primary, 
CH2OH  •  CH2OH,   and    pinacone   (the   isomer  of  hexyl 
glycol)  is  a  double  tertiary,  (CH3)2-COH-COH •  (CH3)2. 
The    chemical   transformations   of  the    glycols    resemble 
those  of  the  alcohols  so  far  as  they  take   place  in  the 
class  radicals,  but  they  are  of  much  greater  variety,  inas- 
much  as   both   hydroxyl   groups,   or   one   only,    may   be 
replaced  by  other  radicals.     The  primary  glycols,  when 
oxidized,  form   two   series  of  acids   (the   lactic  and  the 
oxalic),  and   the   other   alcoholic   derivatives,   aldehydes, 
ethers,  etc. 

Six  glycols  are  known,  colorless,  syrupy  liquids,  solu- 
ble in  water  and  in  alcohol,  which  resemble,  in  mode  of 
formation  and  properties,  ethene  glycol. 


332  ORGANIC  CHEMISTRY. 

645.  Ethene  glycol,  CH2OII  CH2OH,  is  prepared  by 
(1)  heating  a  mixture  of  equal  parts  of  ethene  di-bro- 
mide  and  an  alcoholic  (solution  of  potassium  acetate  for 
several  hours,  in  stout  flasks,  securely  stoppered, 


C2H6-O-C2H8O+CH2OH-CH2-O-C2H8O; 

(2)   separating  out  the  ethene  acetate,  and   then  (3)  de- 
composing it  by  potassium   hydrate  and  distilling, 


CH2OH  •CII20-C2H30 

K()(12II30  +  CH2OII-CII2OH. 

Ethene  glycol  is  a  colorless,  sweetish  liquid,  of  the  con- 
sistency of  a  thin  syrup,  having  an  odor  somewhat  like 
that  of  ethyl  alcohol.  Sp.  gr.,  1.125;  boils  at  197°C.  It 
is  sparingly  soluble  in  ether. 

It  yields  a  groat  variety  of  substitution  products;  e.  g.,  it  is  ox- 
idized by  cold  nitric  acid  to 

CH2OH  •  CII2OII  +  O,  =  H20  +  CH2OH  CXX)II  =  t/lyroUic  acid, 
which  is  half  alcohol  and  half  acid,  and  by  heated  nitric  acid  to 
CH2OH  •  CH2OH  +  O4  =  2H2O  +  COOII  ('CK)H  =  oxalic  acid.  It 
forms  compound  ethers  with  the  alcohol  radicals;  as, 

CH2OII     CH,O    C2H5=-ethylic  ethenate; 
ethereal  salts,  with  acid  radicals  ;  as, 

CH2OH    CH2O    C2H3O  —  ethene  acetate; 

and  a  peculiar  variety  of  simple  ethers,  called  poly-ethenic  alco- 
hols, by  abstraction  of  water  and  condensation  of  two  or  more 
molecules;  as,  2(C2H4(OH)2)  —  H2O  =  C2H4OH  O  •  C2H4OH. 

646.  Two  tri-hydric  alcohols,  or  glycerols,  are  known, 
of  the  general  formula  (CnH2n_1)'"(OH)3-  The  onl>T  one 
of  importance  is  usually  called 

GLYCERIN,  C3H8O3  =  CH2OH  •  CHOH   CH2OH, 

which  may  be  obtained  from  most  of  the  fixed  oils  and 
fats  by  saponification.  These  substances  are  ethereal 
salts  containing  the  trivalent  propenyl,  C3H5,  and  three 


THE  ALCOHOLS.  333 

monovalent  acid  radicals  belonging  to  the  fatty  and  the 
oleic  series.  Mutton-suet  is  largely  tri -stearin  (a  solid), 
C3H5  •  O3  :  (C18H35O)3  ;  palm-oil  is  nearly  tri-palmi- 
tin,  C3H5  !  O3  i  (C16H31O)3;  and  olive-oil  is  princi- 
pally triolein,  C3H5  •  O3  i  (C18H88O)8. 

The  ordinary  fatty  substances  contain  mixtures  of  these  and 
their  homologues.  All  of  them  decompose  when  boiled  with  strong 
bases.  The  acids  unite  with  such  bases  to  form  a  soap,  and  glycerol 
is  liberated.  The  usual  process  consists  in  decomposing  such  fats 
by  superheated  steam;  as, 

C3H6=0=(C18H350)3  +  3H20=3(C18H350    OH)  +  C3H5(OH)3. 

Pure  glycerol  is  a  sweet,  viscid  liquid,  which  boils  at 
290°C.  and  solidifies  at  very  low  temperatures.  When 
strongly  heated,  it  decomposes  into  2H2O  and  acrolein, 
an  aldehyde  causing  the  irritating  odor  noticed  when 
grease  is  dropped  on  a  hot  stove.  Glycerol  has  consid- 
erable solvent  powers,  does  not  easily  oxidize  nor  evap- 
orate,— qualities  which  render  it  valuable  to  pharmacists 

647,  Glycerol  may  be  oxidized  to  gly eerie  acid, 
CH2OH  •  CHOH  •  COOH, 

but  is  usually  decomposed  by  oxidizing  agents  to  formic 
and  oxalic  acids. 

It  may  give  rise  to  three  series  of  substitution  prod- 
ucts according  as  one,  two,  or  three  hydroxyl  groups 
are  replaced  by  other  radicals.  The  ethers  so  formed 
have  names  ending  in  "in."  For  example,  HC1  converts 
it  first  to  mono-chlorhydrin,  C3H5(OH)2C1,  then  to  di- 
chlorhydrin,  C3H5OHC12;  finally  PC15  forms  with  this 
tri-chlorhydrin,  C3H5C13.  Fuming  nitric  acid  produces 
with  it  tri-nitro-glycerin,  C3H5-O3-  (NO2)8,  a  heavy,  oily 
liquid,  which  burns  quietly  when  inflamed  by  a  lighted 
fuse,  but  which  explodes  with  fearful  violence  by  per- 
cussion.1 It  is  a  constituent  of  dynamite  and  other  ex- 
plosives. 


334  ORGANIC  CHEMISTRY. 

When  glycerol  is  heated  in  scaled  tubes  with  acids,  it  yields 
ethereal  salts,  which  are  called  glycerides;  thus,  there  are  three  acetins; 

Mono-acetin,  (C3H5)(OH)2  •  O  •  C2H3O; 
Di-acetin,   (C3H5)(OH)  :  O2  :   (C2II3O)2; 
Tri-acetin,  (C3II5)  :  O3  :  (C2H3O)3. 

In  this  way,  the  stearin,  palmitin,  and  olcin   of  natural   fats  have 
been  produced  artificially. 

648.  Erythrite,  C4H6(OH)4,  the  only  tetrahydric  al- 
cohol  known,  exists   in    erythrin,  a   constituent    of  sev- 
eral  coloring   matters.     It  forms  colorless,  sweet-tasting 
crystals. 

649.  Mannite,  O6II8(OII)fi,  and  its  isomer,  dulcite,  are 
hexahydric  alcoliols,  and   are  sugars  found    naturally  in 
certain  plants. 

Mannite  is  obtained  in  needle-like  crystals,  not  fer- 
mentable, from  the  dried  sap  of  the  manna  ash.  It 
may  also  be  produced  artificially  from  glucose  by  nas- 
cent hydrogen,  C6Ill  2O6-fII2=C6H14O6. 

The  structural  formulae  following  show  its  oxydation  by  two 
stages  to  mannitic  and  saccharic  acids: 

CIIOII     CIIOII     CII2OH, 
Mannite, 

CHOH    CHOH    CH2OH. 

CHOH     CIIOII     CH2OH, 

Mannitic  acid, 

CHOH  CHOH  •  COOH. 

CHOH  •  CHOH  COOH, 

Saccharic  acid,      .         .         | 

CHOH     CHOH    COOH. 

Dulcite  oxidizes  to  mucic  acid,  which  is  isomeric  with  saccharic 
acid.  These  two  acids  are  generally  obtainable  by  the  oxidation 
of  the  various  carbohydrates  with  nitric  acid. 


RECAPITULATION.  335 


Recapitulation. 

The  alcohols  are  found  in  three  metameric  forms,  containing 
CH2OH  (primary),  CHOH  (secondary),  and  COH  (tertiary),  radi- 
cals. 

In  each  of  these  forms,  true  isomers  are  possible,  as  in  the  case 
of  arnyl  alcohol. 

The  primary  alcohols  oxidize  first  to  aldehydes,  then  to  acids. 
The  secondary  alcohols  oxidize  to  ketones. 

The  tertiary  alcohols  break  up  upon  oxidation,  forming  two 
acids  of  lower  carbon  content. 

Alcohols  are  also  grouped  according  to  the  number  of  hydroxyl 
radicals  they  contain:  the  carbinols,  one  OH;  the  glycols,  two  OH; 
the  glycerols,  three  OH,  etc.  Also,  with  reference  to  their  alkyl 
radical ;  as,  CMH2n+i  (methyl  series) ;  CwH2n-i  (allyl  series),  etc. 

The  ordinary  alcohol  is  eihylic,  found  in  fermented  liquors,  like 
ale,  beer,  and  wine;  in  ardent  spirits,  like  whiskey;  in  high  wines, 
and  pure  in  absolute  alcohol. 

Two  theories  of  fermentation  are  presented:  Pasteur's,  which 
supposes  the  presence  of  living  plants  and  animals;  Liebig's,  which 
is  based  upon  molecular  disturbances;  and  two  sets  of  ferments  are 
recognized,  the  soluble  and  the  organized. 


CHAPTER    XXI. 

THE    CARBOHYDRATES. 

650.  The  carbohydrates,  Cy(H2O)x,  are  widely  distrib- 
uted in  the  vegetable  world,  and  play  a  most  important 
part  in  the  life  of  a  plant,  which  forms  starches,  sugars, 
or  gums,  according  to  its  apparent  needs. 

They  form,  naturally,  numerous  isomers,  which  yield  to  the 
chemist  products  so  intimately  related  aft  to  indicate  a  close  rela- 
tionship. Their  aqueous  solutions  are  generally  optically  active. 
Most  turn  the  plane  of  polarization  to  the  right  (dextrose),  but 
not  to  the  same  extent;  a  few,  as  laevulose  and  inulin,  strongly 
to  the  left.  They  are  neutral  bodies,  containing  both  alcoholic 
(CH2OII  or  CHOI!)  and  aldehydic  radicals  (HOC),  and  are,  there- 
fore, readily  oxidized.  When  oxidized  with  nitric  acid,  all  yield, 
as  a  final  product,  oxalic  acid;  but,  in  the  intermediate  stages, 
saccharic  or  inucic  acids,  and  frequently  also  formic  acid.  It  must 
be  noted  that  they  do  not  contain  uater  as  such,  although  they 
contain  II  and  O  in  the  proportion  (H2O)Z. 

651.  The  carbohydrates  from  three  groups.     I  GROUP. 

The  glucoses,  C6II12O6,  are  alcoholic  aldehydes, 

CH2OII(CHOH)4CH:0. 

They  include  mannitose,  dextrose,  lacvulose,  maltose,  lac- 
tose;— all  of  which,  in  contact  with  yeast,  pass  into  vinous 
fermentation,  and  several  others  little  known,  not  fer- 
mentable ;  as,  inosite  (existing  in  muscular  flesh),  and 
sorbin  (from  mountain  ash  berries).. 

II  GROUP.  Saccharoses,  C12H22O11,  have  not  been  ob- 
tained artificially,  and  are  not  fermentable.  On  long 
boiling  with  dilute  sulphuric  acid,  they  suffer  " inversion" 

(336) 


THE  CARBOHYDRATES. 

absorbing  a  molecule  of  water,  and   forming  a  mixture 
of  the  two  fermentable  glucoses;  as, 


Cane  sugar.  Dextrose.  Lsevulose. 

They  may,  therefore,  be  regarded  as  anhydrides  of  di- 
glucose.  They  include  cane  sugar,  malt  sugar,  milk 
sugar,  and  less  important  isomers. 

Ill  GROUP.  Amyloses  (C6H10O5)X,  are  tasteless  bodies, 
which  are  converted  into  the  glucoses  by  diastase  or 
by  boiling  with  sulphuric  acid,  acting  in  this  respect  as 
anhydrides  of  the  sugars.  Their  molecular  weight  is 
thought  to  be  double  or  treble  that  of  their  empirical 
formulae.  They  form  several  sub-groups:  cellulose  and 
tunicin  ;  starch,  inulin,  and  glycogen;  dextrin;  gum  and 
mucilage,  and  pectin. 

652,  Cellulose,  3C6II10O5,  forms  a  large  proportion  of 
the  solid  parts  of  plants.  It  is  well  represented  by  pu- 
rified vegetable  fiber,  such  as  filter  paper.  Pure  cellu- 
lose is  white,  translucent,  insoluble  in  water,  alcohol, 
and  ether,  not  acted  upon  by  dilute  acids,  nor  by  alka- 
lies, and  is  quite  innutritions.  It  dissolves  in  an  am- 
moniacal  solution  of  basic  cupric  carbonate,  from  which 
it  is  precipitated  in  white  flakes  by  acids.  Cellulose  is 
not  colored  by  iodine. 

Transformations.  In  cold,  concentrated  sulphuric  acid, 
cellulose  is  converted  to  a  jelly-like  mass,  which,  if 
thrown  into  a  large  quantity  of  water,  deposits  white 
flakes  of  an  isomer,  called  amyloid,  because  it  is  colored 
blue  by  iodine.  By  a  longer  contact  with  the  strong 
acid,  the  cellulose  changes  to  a  second  isomer,  dextrin  ; 
finally,  upon  boiling  the  solution,  the  dextrin  assimilates 
water  and  changes  to  glucose. 

If  unsized  paper  be  dipped  for  a  few  seconds  in  a  cold^ 
mixture  of  two  volumes  of  strong  H2SO4,  and  one  volume 

Chem.—  22. 


338  ORGANIC  CHEMISTRY. 

of  H2O,  the  surface  becomes  converted  to  amyloid.  If 
the  paper  be  now  thoroughly  washed,  it  will  be  found 
to  have  become  tougher,  and  is  not  softened  by  water. 
It  is  sold  as  a  substitute  for  parchment,  under  the  name 
of  parchment  paper. 

653.  The  cellulo-nitrins   are   made   by  steeping  finely- 
divided   cellulose    in    a    mixture   of   nitric  and    sulphuric 
acids,  and   subsequently  washing  and    drying  the   prod- 
ucts, which    have   increased   in  weight   without  undergo- 
ing any  change  in  external  appearance.      Several  nitryl 
(NO2)  substitution    products  may  be    formed,  depending 
partly  <>n  the  strength    of  the  acids,  and    partly  on  the 
time  consumed. 

With  two  parts  of  the  strongest  nitric  and  one  of  sul- 
phuric acid,  tri -nitrocellulose  forms,  06H7O5(NO2)3. 
This  is  gun-cotton  or  pyroxylin,  four-fold  as  explosive 
as  gunpowder,  employed  to  some  extent  in  the  Austrian 
service,  and  in  blasting.  It  is  insoluble  in  alcohol  and 
ether.  Less  highly  nitrated  compounds  arc  less  explo- 
sive, but  are  soluble  in  a  mixture  of  ether  and  alcohol, 
producing  collodion.  This  solution  of  collodion  evapor- 
ates speedily,  leaving  a  transparent,  flexible,  and  adhe- 
sive film,  which  is  largely  used  in  making  photographic 
negatives  on  glass. 

Tunicin  is  animal  cellulose,  occurring  in  the  mantle  of  ascidians. 

654.  Starch,  (C6H10O5)3,  is  found   in  the  cells  of  all 
growing  plants,  most  abundantly  in  certain  seeds  (cereal 
grains,   rice,    chestnuts),    in    soft   stems    (sago-palm),    in 
roots   (arrow-root  and   tapioca),  and   in  tubers  (potato). 
It  is  prepared  by  reducing  the  vegetable  structure  to  a 
pulp,  and    washing  with    much    cold  water  upon   a  fine 
sieve.     The    cellular   tissue    remains    behind,   the    starch 
passes   through    with    the  water   and    soon    settles    as   a 
white  sediment.     It  is  then  washed  and  dried  at  about 


THE  CARBOHYDRATES. 


339 


140°F;  but  still  retains  considerable  hygroscopic  water 
(10  to  18%),  and  small  quantities  of  wax  and  fat. 

When  the  various  sorts  of  starch  are  examined  under 
the  microscope,  they  are  found  to  consist  of  minute  ovoid 
granules,  which  appear  to  be  made  up  of  concentric  lay- 
ers, covered  with  an  exceedingly  delicate  envelope  of 
cellulose.  The  granules 
from  different  plants  vary 
in  size  and  shape,  those 
from  the  potato  having 
four  times  the  diameter 
of  those  from  wheat  and 
rice.  See  Fig.  103. 

When  heated  in  a  little  wa- 
ter above  60°C.,  the  envelopes 
burst,  and  the  starch  appears 
to  dissolve,  but,  on  cooling,  it 
settles  to  a  jelly  -  like  mass 
(starch  paste),  which  may  be  FlG 

dried    to    a    hard,  transparent 

mass.  After  long  boiling,  starch  no  longer  gelatinizes,  but  is  con- 
verted to  soluble  starch.  All  forms  of  starch  are  characterized  by 
forming,  with  traces  of  iodine,  a  beautiful  blue  color.  When  starch 
is  boiled  in  water  containing  diastase,  or  a  very  small  amount  of 
sulphuric  acid,  it  changes  first  to  soluble  starch,  then  to  dextrine, 
and  finally  to  dextrose.  It  is  oxidized  by  nitric  acid  to  saccharic 
and  oxalic  acids,  and  forms,  with  concentrated  nitric  acid,  xyloidin, 
C6H9NO2O5,  an  inflammable  body,  resembling  gun-cotton. 

The  uses  of  starch  in  the  laundry  are  well  known.  Raw  starch 
is  digested  with  difficulty;  on  the  other  hand,  cooked  starch  is  very 
wholesome,  and  is  an  important  article  of  food. 

655.  Bread-making.  Wheat  flour  contains  about  60% 
of  starch,  10%  of  dextrine  and  sugar,  and  10^  of  a  ni- 
trogenous substance  called  gluten.  When  flour  is  mixed 
with  about  half  its  weight  of  water,  it  forms  a  dough, 
which  is  tenacious  in  proportion  to  the  gluten  it  con- 
tains. This  dough  baked  is  unleavened  bread,  unpalata- 
ble and  difficult  of  digestion.  But  if  the  dough  be  dis- 


340  ORGANIC  CHEMISTRY. 

tended  by  carbonic  anhydride,  it  forms  a  porous  sponge, 
which  (after  kneading  to  render  the  cavities  of  uniform 
size)  is  baked  at  a  temperature  sufficient  to  burst  the 
starch  granules,  and  convert  a  portion  of  them  to  dex- 
trin, and  becomes  bread. 

The  carbonic  anhydride  necessary  for  " aerating"  the 
sponge  is  obtained  in  many  ways;  the  oldest  by  means 
of  vinous  fermentation  set  up.  primarily,  in  the  sugar  of 
the  flour,  and  afterwards  in  the  starch  by  putrefaction 
of  old  dough  or  leaven,  or  by  warm  mixtures  of  salt  and 
water;  and,  secondly,  by  yeast,  whose  action  has  already 
been  described;  thirdly,  obtained  from  the  decomposition 
of  an  alkaline  bicarbonate  by  some  acid  or  acid  salt,  such 
as  the  lactic  acid  of  sour  milk,  tartaric  acid,  cream  of  tar- 
tar, super-phosphate  of  lime,  etc.  ;  bakintj  powdery  are 
mixtures  of  this  sort.  Bicarbonate  of  ammonia  is  some- 
times used  alone  by  cake-bakers.  Fourthly,  by  forcing 
the  gas  or  air  through  the  dough  by  mechanical  contriv- 
ances, "  aerated  bread."  On  baking,  the  carbonic  acid 
and  alcohol,  which  have  formed,  are  driven  off.  Good 
bread  contains  about  40%  of  water.  The  apparent  dry- 
ing of  stale  bread  does  not  consist  wholly  in  loss  of 
water,  but  also  in  an  internal  change  in  the  particles  of 
the  bread.  A  stale  loaf  gently  heated  in  a  closed  vessel 
for  an  hour  regains  the  properties  of  new  bread. 

656.  Iceland   moss,  inulin,  and   glycogen    are   starch- 
like   substances,  which   are   not  colored   blue   by  iodine. 
Inulin  obtained  from  dahlia  tubers  and  roots  of  the  dan- 
delion, changes   by   boiling  with    dilute  acids   into   pure 
laivulose.     Glycogen,  an  animal  starch  found  in  the  liver 
of  several  animals,  changes  with  great  rapidity  into  dex- 
trose by  the  action  of  saliva. 

657.  Dextrin,  C6H10O5,  is  formed  from  starch  by  the 
action  of  diastase,  and  also  by  "boiling  with  dilute  acids. 
It  is  best  manufactured  by  moistening  starch  with  water 


THE  CARBOHYDRATES.  341 

containing  2%  of  nitric  acid,  drying  and  finally  roasting 
to  110°.  Dextrin  is  a  yellowish  powder,  freely  soluble 
in  water,  and  not  changed  blue  by  iodine.  Its  solution 
turns  the  plane  of  polarization  strongly  to  the  right, 
whence  its  name. 

It  is  the  gum  used  on  postage  stamps,  under  the  name  of  "  Brit- 
ish gum."  It  is  extensively  used  in  calico  printing  for  thickening 
mordants  instead  of  the  true  gums. 

658.  The  gums  are  mixtures  of  amorphous  brittle  bod- 
ies,  the   dried   exudation    from   many    plants.     The   best 
known  are  from  the  acacias;  viz.,  gum  arabic  and  gum 
Senegal.     These  contain  from  70  to  80  per  cent  of  arabin, 
CjgH^Ojj,  soluble    in    water,  but    changing    on    being 
heated  to  130°C.  to  metarabin  (Cell^O,;),,  which  swells 
up  to  a  jelly-like  mass  in  water,  but  does  not  dissolve. 
Arabin  and  metarabin  are  common  in   plants,  as  in  the 
exudations  from  cherry  and  plum  trees. 

Bassorin  is  found  frequently  mixed  with  arabin,  as  in 
peach-tree  gum.  It  forms  with  water  a  gelatinous  mass, 
which  is  a  mucilage.  It  is  the  principal  constituent  of 
Gum  Tragacanth.  Other  mucilages,  as  those  found  in 
mallows  and  linseed,  are  isomers  of  starch,  but  are  solu- 
ble in  water. 

659.  Pectose  and  pectin  are  found  widely  distributed 
in  plants.     Pectose  (which  is  insoluble  in  water)  in  un- 
ripe, fleshy  fruits  and  roots,  is  converted  by  fermentation 
to   pectin,  a    soluble   substance   which   is   found    in    ripe 
fruits,  and  which   gives   to  their  juices  the   property  of 
gelatinizing    when    boiled    (currant    jelly).      It    readily 
changes  to  other  gelatinous  bodies,  and  finally  to  meta- 
pectic  acid,  which  is  very  nearly  arabin. 

660.  Glucose,  or  grape -sugar,  is   found  in  most  ripe 
sweet   fruits.      It  generally   contains   two    isomers,   dex- 
trose and  Isevulose,  which  differ  principally  in   the  fact 


342  ORGANIC  CHEMISTRY. 

that  solutions  of  dextrose  turn  the  plane  of  polarized 
light  to  the  right  (-f  56°),  and  of  laivulose  to  the  left 
( — 104®).  Inverted  sugar  is  a  mixture  of  equal  mole- 
cules of  both,  found  naturally  in  honey,  and  produced 
from  cane  sugar  by  ferments,  by  boiling,  etc. 

Dextrose  (ordinary  glucose),  C6II12O6,  is  found  in  di- 
abetic urine.  As  already  noted  (p.  H27)  it  is  produced 
in  germinating  seeds  by  the  action  of  diastase  upon 
starch.  It  is  prepared  in  large  quantities  by  boiling 
starch  with  dilute  sulphuric  acid, 

starch,  (',.  II ,  „<)-  f  TT2O  ^  CJIj  2O6,  glucose. 

After  some  hours,  chalk  is  added  to  neutralize  the  acid, 
and  the  solution  is  drawn  off.  On  concentrating  the 
liquid  to  a  syrup,  the  dextrose  crystallizes  in  cauliflower- 
like  masses. 

Glucose  dissolves  in  1.2  parts  of  cold  water.  It  is  less 
sweet  than  invert  sugar,  and  much  less  than  cane  sugar. 

Like  other  aldehydes,  the  glucoses  are  strong  reducing  agents, 
especially  when  wanned,  reducing  the  nohle  metals  easily — bis- 
muth, copper,  etc.,  in  alkaline  solutions.  Feh  ling's  solution,  con- 
taining cupric  tartrate.  dissolved  in  caustic  alkali,  is  an  excellent 
test  for  glucose,  producing  the  red  cuprous  oxide,  Cu2O,  on  heat- 
ing, § 468.  Cane  sugar  does  not  produce  this  reaction  until  it  has 
suffered  inversion.  On  oxidizing,  the  glucoses  are  changed  to  sac- 
charic acid. 

Laavulose,  C6II12O6,  or  fruit  sugar,  C6H12O6,  H2O, 
may  be  obtained  pure  from  inulin  by  the  same  methods 
that  dextrose  is  obtained  from  starch.  Also  by  treating 
invert  sugar  with  milk  of  lime,  which  forms  an  insoluble 
lime  salt  with  Ia3vulose,  and  not  with  dextrose. 

Laevulose  exhibits  the  same  chemical  characters  as  dextrose,  but 
is  less  easily  fermented.  Most  of  their  products  are  identical. 
When  heated  to  about  170°C.,  dextrose  and  laevulose  each  lose 
a  molecule  of  water,  and  form  glucosan  and  IcKvulosan,  C,.lllQO5. 
These  are  obtained  from  cane  sugar  also.  On  heating  any  sugar 


THE  CARBOHYDRATES.  343 

to  about  200°C.  a  brown  mixture,  called  caramel,  is  produced,  but 
at  higher  temperatures  the  sugars  are  completely  decomposed. 
Mannitose  is  optically  inac^ve,  but  in  other  respects  resembles 
laevulose. 

661.  The  glucosides  are  substances  widely  distributed  in 
the  vegetable  world,  which  so  far  resemble  the  ethereal 
salts  that  they  are  resolved  by  boiling  with  dilute  acids, 
as  also  by  contact  with  ferments  into  some  sort  of  sugar, 
which  is  generally  glucose,  and  to  other  compounds.    For 
example,  amygdalin,  020H27NO11,  found  in  the  kernels 
of  bitter   almonds,  peaches,  etc.,  by   boiling  with    dilute 
HC1,   assimilates   II 2O,  and   forms   glucose,  prussic   acid, 
and  the  oil  of  bitter  almonds  ;  thus, 

C20II27N011  +  H20  =  2(C6H1206)+HCN+C6H5CHO. 

The  same  change  takes  place  when  the  juice  of  crushed 
almonds  is  exposed  to  the  air,  by  reason  of  a  natural  fer- 
ment, emulsin,  which  is  also  contained  in  the  almond. 
Among  the  most  important  of  the  glucosides  are  indican 
and  ruberythric  acid  (the  sources  of  indigo  and  madder)  ; 
valuable  medicinal  agents,  like  jalapine  and  digitaline; 
and  poisons,  like  solanine  and  antiarine. 

662.  Lactose,  C6H12O6,  is   obtained   by  inversion   of 
milk  sugar.     It  contains  two  sugars,  one  of  which  resem- 
bles dextrose,  producing  saccharic  acid  on  oxidation  ;  the 
other  yielding   mucic  acid.     Both   are   fermentable,  and 
reduce  Fehling's  solution. 

663.  Saccharose,  C12H22O1;l,  or  cane  sugar,  is  found 
to  some  extent  in  the  juices  of  nearly  all  plants;   very 
abundantly  in  sorghum,   maple  sap,  beet-roots,  and  the 
sugar-cane.     It  is  prepared  from  the  crude  juices  of  such 
plants  by  (1)  neutralizing  with  0.5%   of  milk  of  lime  to 
prevent   inversion;    (2)  boiling  to   coagulate  albuminous 
substances;    (3)    filtering    through    thick    layers   of  ani- 
mal charcoal  to  remove  these  and  the  coloring  matters; 


344  ORGANIC  CHEMISTRY. 

(4)  evaporating  in  racuo  as  rapidly  and  at  as  low  a 
temperature  as  possible.  (5)  When  the  solution  has  be- 
come sufficiently  concentrated  to  crystallize  on  cooling, 
it  is  drawn  into  pans  and  stirred,  so  as  to  promote  the 
formation  of  a  granulated  sugar.  (G)  This  raw  sugar  is 
finally  drained  from  a  portion  that  is  not  crystallizable, 
and  which  is  molasses.  Raw  sugar  is  refined  by  a  second 
or  third  treatment  with  bone  black,  forming  white  sugar 
and  residues  of  syrups. 

Cane  sugar  is  soluble  in  ^  of  its  weight  of  cold  water. 
It  may  be  obtained  from  its  solution  by  slow  evaporation 
in  large  monoclinic  prisms  (rock  candy).  When  heated 
to  1()0°C  it  melts,  and,  on  cooling,  forms  an  amorphous 
transparent  mass  (lemon  candy). 

Cane  sugar  is  at  once  decomposed  by  strong  sulphuric  acid, 
evolving  much  S()2,  and  formic  acid,  II  -COOH,  and  blackening 
from  separation  of  carbon  (distinction  from  glucose).  Distilled 
with  Mn()2  and  II2SO4  it  yields  formic  acid  more  abundantly. 
It  is  interesting  to  note  that  glucose  is  a  polymer  of  formic  alde- 
hyde, C'II20. 

664.  Milk  sugar,  C,  2H22Oj  l  -f  H2O,  is  found  only  in 
the  milk  of  animals.  When  the  whey  of  milk  is  evap- 
orated to  a  syrup,  and  allowed  to  stand  for  some  time, 
the  sugar  of  milk  forms  in  crusts.  It  is  soluble  in  six 
parts  of  cold  water,  and  is  harder  and  less  sweet  than 
cane  sugar. 

It  resembles  cane  sugar  in  most  chemical  reactions, 
reducing  silver  and  copper  salts  slowly,  and  is  resolvable 
into  fermentable  sugars.  These  lactoses  yield,  on  fer- 
mentation with  cheese,  both  alcohol  and  lactic  acid.  The 
Kalmucks  prepare  an  intoxicating  drink,  called  koumiss, 
from  the  milk  of  mares. 

Maltose,  isomeric  with  milk  sugar,  is  found  in  malt 
extract,  as  an  intermediate  stage  in  the  conversion  of 
starch  to  glucose. 


RECAPITULATION.  345 


Recapitulation. 

(1)  The  carbohydrates,  the  starches,  the  true  gums,  and  cellulose, 
and  the  various  sorts  of  sugar,  are  among  the  natural  products 
of  most  plants. 

(2)  The  structural  formulae  of  none  of  them  are  certainly  known. 

(3)  Upon  oxidation  they  all  yield  oxalic  acid,  with  various  inter- 
mediate products,  like  mucic  and  saccharic  acids. 

(4)  Optically,  they  are  mostly  dextrogyrate;  a  few  are  laevogyrate. 

(5)  The   starches,  gums,   and   cellulose    are    tasteless.     Mannite   is 
sweetish,  glucose  rather  sweet,  and   the  saccharoses  "sweet  as 
sugar." 

(6)  Those  that  act  reducing,  resemble  the  aldehydes;  e.  g.,  glucose. 
Those  that  resemble  mannite  are  alcohols.     Most  are  aldehy- 
dic  alcohols. 

(7)  All    seem    to    contain    the    six    carbon    group,    with    varying 
amounts  of  H  •  O  •  H. 

(8)  The  numerous  isomers  of  the  glucoses  are,  perhaps,  polymers 
of  formic  aldehyde,  H     CH  :  O. 

(9)  The  starches,  gums,  mucilages,  cellulose,  and  pectin  are  meta- 
mers  (C6H10O5). 

(10)  In  beer-making,  the  starch  is  changed  to  glucose,  this  to   al- 
cohol and  carbonic  anhydride. 

(11)  In  ardent  spirits,  the  alcohol  is  produced  from  fermented  marc 
or  is  distilled  from  mash. 

(12)  In  bread-making,  the   other   product  of  fermentation,  CO2,  is 
utilized  to  distend  the  gluten  of  the  flour. 

(13)  The  baking  powders  obtain  the  CO2  by  decomposing  NaHCO3 
by  acids,  or  by  acid  salts. 


CHAPTER   XXII. 

ALDEHYDES    AND    KETONES. 

665.  These  compounds  are  derived  from  the  alcohols 
by  oxidation.  When  a  primary  alcohol  is  treated  with 
chromic  mixture,  it  is  oxidized  in  two  stages. 

(1)  II2   is  removed   from    the  (1H2<)Il    group,  the   hy- 
droxyl  is  broken   up,   and  the   product  formed   is  an   al- 
dehyde; as,  ('H3riI2OII+0  =  CH3,  II-CO+II20. 

(2)  The    aldehydes    oxidize   very    readily   to   (icids,  in 
which  the  hydroxyl  group  is  restored;  as, 

C1I,  H-CO-    O  =  CH-COOH. 


(3)  If  an    alkaline    salt   of  such    an    acid    is   strongly 
heated,  a  kctonc  is  formed, 

(CH8COOXa)2  =  Na2C08  +  CII3-CO-CH3. 

(4)  The  kctoncs  are  also  produced   by  the  direct  ox- 
idation of  the  secondary  alcohols;   II  2  being  eliminated 
from  the  CIIOH  group. 

These  aldehydes,  acids,  and  ketones  contain  at  least  one  alkyl 
radical,  CHH2n+i,  etc.,  united  by  carbonyl,  CO,  to  some  other  radical; 
as,  H,  OH,  or  CH3.  Their  relationship  will  be  clearly  seen  by  in- 
spection of  these  formulae: 


CH3 

CH3 

CH3 

CH3              CH3 

1 

1 

1 

1                    1 

CH2 

c=o 

c=o 

C  =  O           CHOH 

1 

1 

1 

1                    1 

OH 

H 

OH 

CH3              CH3 

Ethyl 

Acetic 

Acetic 

Acetone.       Secondary 

alcohol. 

aldehyde. 

acid. 

propyl  alcohol. 

C2H60 

(346) 

C2H40 

C2H402 

C3H60         C3H,0. 

ALDEHYDES  AND  KETONES.  347 

666.  Nascent  hydrogen,  evolved  from  sodium  amalgam 
and  water,  reverses  these  reactions,  converting: 

(1)  Acid  anhydrides  or  chlorides  to  aldehydes;  as, 

CH3  COC1  J-II2  =  HC1  +  CH3-COH; 

(2)  the  aldehydes  to  primary  alcohols, 

CH3COII  +  II2  —  CH3-  CII2OH; 

(3)  the  ketones  to  secondary  alcohols, 

CH3-  CO  •  CH3  +  H2  =  CH3-  CHOH  •  CH3. 

The  last  reaction  affords  a  general  method  for  preparing  the 
secondary  alcohols,  inasmuch  as  a  ketone,  containing  two  different 
alcohol  radicals,  can  first  be  made  by  distilling  a  dry  mixture  of 
sodium  or  calcium  salts  of  two  different  fatty  acids;  as, 

(1)  CH3  •  COONa,  sodium  acetate +C3H7COONa,  sodium  butyrate= 
NaO  •  CO  •  NaO,  sodium  carbonate -f  CH3  •  CO  •  C3H7  = 

methyl  propyl  ketone. 

(2)  CH3-  CO    C3H7  +  H2  =  CH3    CHOH-  C3H7  = 

secondary  propyl  alcohol. 

An  important  exception  is  found  when  one  of  the  salts  so  dis- 
tilled is  an  alkaline  formate.  In  such  a  case  an  aldehyde  will  be 
produced ;  as, 

CH3  •  COONa  +  H  •  COONa  =  Na2CO3  +  CH3  •  CO  •  H. 

667.  The  aldehydes   are  colorless,   volatile   liquids   of 
pungent   odor.      Some  of  the  essential  oils   are   natural 
aldehydes,  as  the  oils  of  meadow  sweet  (spirea),  anise, 
and  bitter  almonds.     Those  of  the  same  series  strongly 
resemble  each  other,  but  exhibit  the   usual  gradational 
characters  of  homologous  compounds. 

All  aldehydes  form  crystalline  compounds  with  the 
acid  sulphites  of  the  alkalies,  easily  decomposed  by  di- 
lute sulphuric  acid  with  the  liberation  of  pure  aldehyde. 
This  reaction  serves  both  as  a  test  for  the  presence  of 
an  aldehyde,  and  also  as  a  means  for  purifying  it.  When 
heated  with  caustic  potash,  the  aldehydes  are  converted 
to  a  hard  mass,  called  "aldehyde  resin." 


348  ORGANIC  CHEMISTRY. 

668.  Formic  aldehyde,  II  •  CH :  O,  is  a  gas,  obtainable 
in  solution  by  carefully  oxidizing  methyl  alcohol.  Very 
probably  it  is  produced  in  the  living  plant  by  the  action 
of  chlorophyl  in  the  sunlight  upon  carbonic  anhydride 
and  water,  (1O2  -f  II2O  =  U2  -f  II  •  CII :  O.  It  polymer- 
i/es  readily,  and  it  is  an  interesting  problem  whether 
some  of  the  numerous  polymeric  compounds  mentioned 
on  page  294  are  not  derived  from  this  source,  and  that 
starch,  cellulose,  etc.,  are  their  condensation  products. 

Acetic  aldehyde,  riI3CII:O.  is  formed  by  oxidizing 
ethyl  alcohol  with  chromic  mixture  and  distilling. 

It  is  a  colorless  liquid,  with  a  pungent,  ethereal  odor, 
which  mixes  with  water  and  alcohol  in  all  proportions; 
Kp.  gr.  O.S;  boils  21  °C.  It  oxidizes  readily  to  acetic 
acid,  reduces  silver  from  an  ammoniacal  solution  of  sil- 
ver nitrate,  the  silver  depositing  on  the  sides  of  the 
vessel  in  a  mirror-like  film. 

All  aldehydes  exhibit  the  characteristics  of  unsaturated  com- 
pounds. (1)  They  readily  oxidize  to  acids  having  the  same  num- 
ber of  carbon  atoms,  and  hence  are  good  reducing  agents.  (2)  They 
show  a  marked  tendency  to  polymerize,  especially  when  not  per- 
fectly pun.-;  thus,  acetic  aldehyde  has  two  polymers,  called  para- 
and  meta-aldehydes,  each  containing  two  or  more  molecules,  and 
reconvertible  to  ordinary  aldehyde  by  heating.  (3)  They  also  form 
condensation  products.  In  the  presence  of  HC1  and  water,  acetic 
aldehyde  gradually  changes  to  aldol,  C4IISO2. 

Aldol  is  converted  to  butylene  glycol  by  the  action  of  sodium 
amalgam,  and  to  oxy-butyric  acid  by  moist  silver  oxide.  It  is 
consequently  the  aldehyde  of  the  latter.  Moreover,  on  being  heated, 
it  loses  a  molecule  of  water  and  condenses  further  to  crotonic 
aldehyde;  thus, 


CH3 
CH-.O 

CH3 
1 
CHOH 

1 
CH2 

CH2OH 

,  Butylene  glycol. 

CH3 
1 
CHOH 
1 
CH, 

CH:0 
Aldol. 

CH, 

CH 

II 
CH 
1 
CH:0 
Crotonic  aldehyde. 

CH3 

CH:O 

Acetic  aldehyde, 

ALDEHYDES  AND  KETONES.  349 

669.  The  chlorine  derivatives  from  aldehydes  in  mix- 
tures  of  alcohol,  acids,  etc.,  are   exceedingly   numerous, 
and  involve  both  radicals,  CH3  and  CH:O.     Dry  chlor- 
ine gas  produces,  from  acetic  aldehyde,  acetyl  chloride, 
CH3-CO-C1.     The  action  of  chlorine  upon   absolute  al- 
cohol   has   been    detailed   on    page   323.      The    tri-chlor- 
aldehyde   which   forms  is  chloral,  CC13-  CHO,  a  volatile 
liquid   of  penetrating  odor;   sp.  gr.  1.5;   boils  at    94°C. 
It  changes,  on  standing,  to  a  porcelain-like  modification, 
para-chloral,  probably  tri-chloral,  which  distills  at  180°, 
becoming  reconverted  to  chloral.     It  is  an  aldehyde,  oxi- 
dizing "to  tri-chlor  acetic  acid,  CC13COOH.     Unlike   the 
other  aldehydes,  it  combines  eagerly  with  water,  form- 
ing  chloral   hydrate,  CC13- CH(OH)2,  which  forms  large 
crystals,  easily  soluble  in  water.     Chloral  and  its  deriva- 
tives are  easily  decomposed  by  alkalies  into  chloroform 
and  a  formate, 

CC1  j-  CHO  +  KHO  =  CHC13  -f  H  -  COOK. 

It  is  similarly  decomposed  by  the  alkalies  of  the  blood 
when  administered  as  a  medicine,  and  produces  deep 
sleep,  but  not  insensibility  to  acute  pain. 

The  higher  aldehydes  of  this  series  have  numerous  isoraeric 
modifications,  like  the  alcohols.  The  most  important  will  be  suf- 
ficiently given  in  connection  with  their  related  compounds. 

670.  Only  two  aldehydes  of  the  next  series,  CJff^CHO, 
are  known. 

Acrolein  is  acrylic  aldehyde,  CH2  :  CH  •  CHO,  best 
prepared  by  heating  glycerol  with  a  dehydrating  agent, 
like  P2O5.  It  is  always  produced  when  a  glyceride  (a 
fat)  is  subjected  to  destructive  distillation. 

Pure  acrolein  is  a  volatile  liquid  boiling  at  52°C,  and 
evolving  vapors,  which  are  exceedingly  irritating.  It 
rapidly  oxidizes  to  acrylic  acid.  Nascent  hydrogen  con- 
verts it  first  to  allyl  alcohol,  and  then  to  propyl  alcohol. 


350  ORGANIC  CHEMISTRY. 

(a)  CII2  :  Oil    Oil :  O  4-  H2  =  CH2  :  CH  •  CII2OH. 

Acrnlei'n.  Allyl  alcohol. 

(b)  CII2  .  Oil   CII2OII-hII2=CII3-Cn2  OII2OII. 

Allyl   alcohol.  I 'ropy  1   alcohol. 

Furfurol,  C4II3O  •  CII :  O,  is  formed  by  heating  sugar, 
bran,  etc.,  with  dilute  sulphuric  acid.  It  is  a  colorless 
liquid,  with  an  agreeable  odor,  like  the  oil  of  cassia.  It 
may  be  converted  to  pyromucic  acid  by  oxidation,  and 
to  furfuryl  alcohol,  C4II3O  •  CII2OII,  by  nascent  hy- 
drogen. 

671.  Only  a  few  aldehydes  of  the  dihydric  alcohols  arc 
known;  theoretically,  they  are  capable  of  yielding  three 
series. 

Glycol  on  oxidation  should  yield  the  following  com- 
pounds, but  the  first  is  unknown : 


I. 

II. 

III. 

IV. 

niijOii 

con 

1 

CII2OII 

con 

1 
con 

con 

1 

coon 

COOII. 

1 

COOII. 

Glycol. 

Glycollic 
aldehyde. 

Glyoxal. 

Glyoxalic 
acid. 

Oxalic 
acid. 

Glyoxal  and  glyoxalic  acid  are  easiest  obtained  by  oxidizing 
ethyl  alcohol  with  nitric  acid.  Glycollic  and  oxalic  acids  are 
formed  by  the  same  reaction. 

On  neutralizing  this  mixture  with  chalk,  the  calcium  salts  are 
formed.  The  oxalate,  being  insoluble,  is  left  behind  on  filtration. 
Alcohol  precipitates  the  glycollate  and  glyoxalate,  and  glyoxal 
remains  in  solution. 

Glyoxal  is  a  deliquescent  solid,  easily  soluble  in  alco- 
hol and  water.  It  is  a  double  aldehyde,  having  the  gen- 
eral character  of  acetic  aldehyde,  reducing  silver  oxide, 
forming  two  aldehyde  ammonias,  glyoxaline,  C3H4N2, 
and  glycosine,  C6H6N4. 


ALDEHYDES  AND  KETONES.  351 

Glyoxallic   acid   is  half   aldehyde   and  half  acid.     As  an   alde- 
hyde, it  acts  reducing,  and  can  be  oxidized  to  oxalic  acid.     It  may 
be  converted  by  nascent  hydrogen  to  glycolic    acid : 
COH    COOH  +  H2  =  CH2OH    COOH. 

672.  The  ketones   are    colorless   liquids   of  a  pleasant 
odor.      Their    boiling    points   and    specific   gravities    in- 
crease somewhat  irregularly  with  their  increase  in  carbon 
atoms.      The   number  of  ketones   possible   by  theory  is 
enormous,  as  any  monovalent  alkyl  radical  may  be  united 
by  CO  to  any  other,  either  alike  or  different,  and  thus 
constitute  a   ketone.     The   ketones   are   metameric  with 
the  oxides  of  the  glycols,  and  also  with  those  aldehydes 
which   contain   the   same  number  of  carbon   atoms;   as, 

(1)  propylene  oxide,  CH3-  CH 

|     >O;and 
CH2 

(2)  acetone,   CH3  •  CO  •  CH3,  are  metameric,  with  propi- 
onic  aldehyde,  C2H5-CO-H.     Those  ketones  which  con- 
tain the  methyl  group,  CH3,  resemble  the  aldehydes  in 
forming    crystalline    compounds    with    potassium    bi-sul- 
phite.     The  ketones  are  more  stable  than  the  aldehydes, 
being  oxidized  with   difficulty  by  chromic  mixture,  and 
then  completely  breaking  up,  yielding  two  acids,  each 
containing   fewer  carbon  atoms  than   the  ketone.     Ace- 
tone yields  formic  and  acetic  acids: 

CH3-CO-CH3+O3  =  H,  COOH  +  CH3,  COOH. 
They  do  not  act  reducing  upon  an  ammoniacal  silver  so- 
lution.    Only  about  thirty  ketones  have  been  thoroughly 
investigated.     The    first,  from   which   they   derive   their 
names,  is  acetone. 

673.  Acetone,    (CH3)2CO,  best   prepared   by  the   de- 
structive distillation   of  calcium   or  lead   acetate.     It   is 
formed  also  by  the  dry  distillation  of  citrates,  tartrates, 
sugar,  starch,  and  wood,  and  on  the  large  scale  as  a  bye 
product  from  the  acetic  acid  and  iron  used  in  prepara- 
tion of  aniline. 


352  ORGANIC  CHEMISTRY. 

Acetone  is  a  clear  liquid  of  peculiar,  pleasant  odor, 
soluble  in  water  and  alcohol;  sp.  gr.,  0.71);  boils  at  55°C. 
It  is  inflammable,  and  burns  with  a  smokeless  flame. 

Nascent  hydrogen  converts  it  to  isopropyl  alcohol  and 
to  pinacone,  (CH8)2CIIO  •  CHO(('II3)2. 

674.  Chlorine  gas  displaces  the  hydrogen  atom  for 
atom  in  successive  stages,  and  forms  six  "chlor-acetones," 
which  are  colorless  "fluids  of  strong  odors.  There  are 
also  numerous  other  derivatives  of  acetone.  Among 
these  are  condensation  products  obtained  by  removal 
of  water  from  two  or  more  molecules;  as, 

3C3H6O—  3II2O  =  C9II12  =  mesitylene, 

a  body  belonging  to  the  benzene  series. 

Methyl-nonyl  ketone,  CH3- CO  •  C9H19,  which  may  be 
formed  artificially,  is  the  chief  constituent  of  the  oil  of 
rue. 

Recapitulation. 

(1)  Numerous  aldehydes  and  ketones  are  metameric,  both  contain- 
ing alkyl  radicals  united  to  carbonyl. 

(2)  The   aldehydes    may  be   reduced    to   primary  alcohols,  or   oxi- 
dized to  acids  of  the  same  number  of  carbon  atoms. 

(3)  The    ketones   may   be    reduced    to   secondary   alcohols,  or   oxi- 
dized to  two  acids  of  less  number  of  carbon  atoms. 

(4)  The    aldehydes    form    compounds  with   ammonia    and    aniline, 
easily  crystallizable ;    the  ketones  do  not. 

(5)  The  ketones  are  more  stable  than  the  aldehydes,  and   are  ca- 
pable of  forming  a  larger  number  of  isomeric  compounds. 


TABLE  OF  PRINCIPAL  ACIDS. 


353 


d       Jf  i  ,J.-I"  - ' 


_o_ 

cf 


1 .  /cl|of 


-ja  SB 

^»r  T  ^   «*^    wot- 

t-<U^o       Q  ,^Q 

O       C  x 

O 


«  O         '5  G 

^    S         "o    » 

w  '  ".sa 


=   a  ' 


Chem.— 23. 


?  B  §«"  i  a  '  - 


,rO 


•«rf 


CHAPTER    XXIII. 

ORGANIC    ACIDS. 

675.  The  organic  acids  agree  only  in  one  particular, 
viz:  the  property  of  forming  salts  when  they  act  upon 
the  oxides  or  carbonates  of  the  metals.  The  reaction 
consists  in  the  exchange  of  one  or  more  atoms  of  hy- 
drogen for  an  equivalent  amount  of  the  metal;  as, 

II('2II302    t-KIIO--.=  Kr2IIa02  +  H2(). 

I.  A  few  organic   acids  contain   hydrogen  directly  united   to  an 
acid  radical,  such  as  prussic  acid,  1ICN. 

II.  Most  organic  acids  contain  hydroxyl  (Oil)  or  its  equivalent, 
hydro-sulphuryl  (SII),  as  in  cyanic  acid,  C'XOII,  or  in  thio-cyanic 
acid,  CNSII. 

III.  Ordinarily,  the    hydroxyl    is    linked    to    carbonyl    CO,  and 
forms  the  complex  monovalent  radical  carbnjryl,  COOII,  and  this  is 
in  turn  united  with  an  alkyl  radical,  as  in  acetic  acid, 

CH3-  CO     Oil  or  CII3,  COOH. 

IV.  The  organic  acids  may  he  reckoned  as  derived  from  the  pri- 
mary alcohols  hy  the  oxidation  of  the  groups  CH2OII;  thus, 

IT,  CH2OH  +  O2  =  H2O  -f  R',  COOH. 

Monohydric  alcohols  give  rise  to  acids  which  are  also  monohy- 
dric  and  monobasic;  as,  CH3,  COOH,  acetic  acid.  Polyhydric  al- 
cohols give  rise  to  polyhydric  acids,  which  may  be  mono-  or 
bi-basic,  etc.;  thus,  glycol  (CH2OH)2  may  give  rise  to  two  di- 
hydric  acids  (1)  glycollic  acid,  CH2OH  •  COOH,  which  contains 
one  alcoholic  group,  CH2OH,  unoxidized;  (2)  oxalic  acid  (COOH)2 
in  which  the  oxidation  is  completed.  The  basicity  of  such  acids 
is  reckoned  by  the  number  of  carboxyl  groups  they  contain,  be- 
cause the  replacable  hydrogen  of  such  acids  is  always  associated 
with  the  radical  carbonyl;  thus  glycollic  acid  is  mono-basic,  and 
oxalic  acid  is  bi-basic. 
(354) 


ORGANIC  ACIDS.  355 

V.  However,  there  are  many  acids  homologous  with  these  that 
have  no  corresponding  alcohol,  but  that  are  derived  from  ethers, 
as-stearic  acid;  and  there  are  still  others  obtained  from  plants  and 
animals  which  can  not  be  referred  to  the  alcohols,  as  the  meconic 
acid  of  opium. 

VI.  Among  the  organic  acids  are  some  which  contain  the  radi- 
cals of  the  mineral  acids,  such  as  sulphurous  acid  H(SO2OH)  and 
hyposulphurous  acid  H(SOOII),  associated  with  an  alkyl  radical. 
Thus,  the  CH3  group  which  is  found  in  acetic  acid  is  also  found 
in  methyl  sulphinric  acid,  CH3SOOH,  and  in  methyl  sulphonic 
acid,  CH3SO2OH.  The  endings,  inic  and  onic,  distinguish  the 
lower  and  higher  state  of  combination. 

676.  The  salts  which  these  acids  form  with  the  metals 
are    (1)    normal   when    all    their   basic    hydrogen   is    ex- 
changed  for  a   metal,  as   potassium   oxalate,  (COOK)2; 

(2)  acid  when  their  basic  hydrogen  is  only  partially  ex- 
changed,  as    acid    potassium    oxalate,    (COOH  •  COOK) ; 

(3)  basic  when  the  acid  radical  does  not  completely  sat- 
urate the  metallic  oxide;  as, 

2(C2H3O),  3PbO,  basic  plumbic  acetate. 

677.  The  ethereal  salts,  which  are  usually  known   as 
the  compound   ethers,  are  formed   by  the   substitution  of 
an  alkyl  radical  in  place  of  the  hydrogen  in  any  one  of 
hydroxyl  groups  of  an  acid;  as,  02H5-  O  •  CH3CO,  ethyl 
acetate  or  acetic  ether. 

Inasmuch  as  glycerol,  C3H5(OH)3,  contains  a  trival- 
ent  radical,  the  glycerine  ethers  may  contain  three 
monovalent  acid  radicals,  which  may  be  alike  or  differ- 
ent. These  take  the  termination  "in;"  as, 

Glycerol,        .  C3H5(OH)3. 

Mono-acetin,  .         C3H5(OH)2C2H3O2. 
Di-acetin,       .  C3H5(OH)(C2H3O2)2. 

Tri-acetin,      .  C3Ho(C2H3°2)3 

678.  Negative  radicals,  such  as  Cl,  CTN",  also  replace  the 
hydrogen  of  organic  acids,  and  in  three  different  ways: 


356  OROAXTC  CHEMISTRY. 

I.  To   form   haloid   compounds  as  in   the   combination 
of  acetic  and   hypoclorous  anhydrides,  producing   chlor- 
acetate=(CH8CO)2O-hCi2O-:2(C2H80,  OC1). 

II.  To    form   acid    HnUdes,   etc.,   by  exchange    of  hy- 
droxyl  for  a  negative  radical,  as   when  the  chlorides  of 
phosphorus  convert  acetic  acid  to  acetyl  chloride, 

PCI 8  -|-  3(CII8COOII)  =P(OH)8  +3(CH8COC1). 

The  acid  radical,  such  as  acetyl  (CH3CO),  in  chemical  operations, 
may  form  acid  anhydrides,  like  acetic  anhydride  (CH3CO)2O,  or 
peroxides,  like  (CII3CO)  O  O  (C'H3CO),  or  acid  anhydrides  con- 
taining two  different  acid  radicals.  All  these  have  their  analogues 
in  inorganic  compounds;  as,  KCl,  chloride;  K  O  •  Cl,  hypochlor- 
ite;  K  ()  K,  anhydride;  K  O  O  K,  peroxide. 

III.  By  exchange  of  an   hydrogen   atom   in  the  alkyl 
radical,  as  when  acetic  acid,  by  the  action  of  chlorine  in 
the  sunlight,  forms  in  succession   mono-chlor-acetic  acid, 
CHjClCOOH;    di-chlor-acetic    acid,    CHCI2COOH;    tri- 
chlor-acetic  acid,  C13CO()II.     These  substances  are  acids, 
•resembling  the  acid  from  which  they  are  derived. 

The  examples  which  have  been  used  are  taken  from 
acetic  acid,  but  we  may  believe  that  all  saturated  or- 
ganic acids  are  susceptible  of  similar  transformations. 
Besides  these,  there  exist  not  only  numerous  isomeric 
modifications,  but  whole  series  of  secondary  and  of  un- 
sut united  acids  derived  from  the  primary. 

679.  The  fatty  acids,  r,tII2nO2  or  C/nII2m+1COOH, 
take  this  name  because  many  of  the  higher  members  are 
found  in  the  natural  fats,  as  ethers  of  glycerol.  They 
may  be  prepared  (1)  from  fats  by  saponification,  or  (2) 
by  decomposing  the  alcoholic  cyanides,  or  (8),  more  fre- 
quently, by  the  oxidation  of  the  monohydric  alcohols. 

The  lower  members  of  the  series  are  volatile  liquids 
of  pungent  odor.  The  members  above  C13  are  not  vol- 
atile, but  may  be  distilled  by  means  of  a  large  volume 
of  steam  which  carries  their  molecules  over  with  it 
mechanically. 


ORGANIC  ACIDS. 


357 


These  acids  after  the  fifth  are  insoluble  in  water,  and 
thereby  take  on  an  oily  character.  Those  above  C10 
are,  at  ordinary  temperatures,  solid  bodies  more  or  less 
resembling  the  fats.  It  may  be  noted  that,  with  the 
succeeding  terms,  we  find  a  decrease  in  specific  gravity, 
but  an  increase  in  boiling  and  in  melting  points,  which 
are  noted  in  the  table  below: 


FATTY  ACIDS. 


CnH2n02,   ACIDS. 

MELTING 
POINT  °C. 

BOILING 

P'NT  °C. 

SP.  GR. 

SOURCE. 

C     II  2  O2,  Formic.      . 

8.5° 

99° 

1.233 

Red  ants. 

C2  H4  O2,  Acetic.        .        17° 

118° 

1.063 

Alcohol. 

C3   11  6  O2,  Propionic.  . 

—21° 

140.5° 

.991 

Ethyl  cyanide. 

C4  1I8  O2,  Butyric.     . 

O 

163° 

.958 

Sugar  and  cheese. 

C5  H10O2,Valeric,(iso) 

—16 

185° 

.947 

Amyl  alcohol. 

C6  H12O2,  Caproic.     . 

90 

205° 

.945 

Cocoa-nut  oil. 

C.  H14O2,  (Enanthylic. 

-10° 

224° 

.934 

Castor-oil. 

C8  H16O2,  Caprylic.     . 

16.5° 

236° 

.914 

Cocoa-nut  oil. 

C9  H18O2,  Pelargonic. 

12.5° 

253°         .906 

Oil  of  rue. 

C10H2002,Capric.        . 

30° 

270°         .930 

Fusel-oil. 

. 

. 

at  100  mm 

. 

CllH22O2,  Undecylic  . 

28.5° 

212.5° 

. 

. 

C12H24O2,  Laurie. 

43° 

225° 

.883 

Bayberries. 

C13H26O2,  Tridecylic  . 

45° 

236° 

. 

C14H28O2,  Myristic.     . 

54° 

248° 

Nutmeg  butter. 

C15H30O2,  Pentadecylic 

51° 

257° 

. 

C16H32O2,  Palmitic.    . 

62°        268.5° 

Palm-oil. 

C17H34O2,  Margaric.   . 

66° 

. 

. 

Cetyl  cyanide. 

C18H36O2,  Stearic. 

69.2° 

287° 

.74 

Tallow. 

C19H38O2,  Medullic.    . 

72.5° 

. 

Ox-marrow. 

C20H40O2,  Arachidic  . 

75°        . 

Pea-nuts. 

C21  

. 

C22H44O2,  Behenic. 

76° 

Oil  of  Ben. 

C25H50O2,  Hyaenic. 

77° 

Hysena  fat. 

C27H54O2,  Cerotic. 

79°    .. 

Bees-  wax. 

C30H6002,  Melissic.     .  i     91°        .         .  1  .       .    Bees-wax. 

CnH2n02,      . 

.     .        .  j  . 

358  ORGANIC  CHEMISTRY. 

680.  Formic  acid,  II  •  COOH,  is  found  free  in  stinging 
nettles.  It  received  its  name  because  it  was  first  ob- 
tained by  distilling  ants  (formica  rufa).  It  is  a  frequent 
product  of  the  oxidation  of  organic  substances,  especially 
the  carbohydrates,  but  is  easiest  obtained  from  oxalic 
acid  (COOH  •  COOH  =  CO2  +  H  •  COOH).  Very  con- 
centrated glycerol  is  heated  to  110°,  and  a  small  quan- 
tity of  crystallized  oxalic  acid  added.  (1)  Mono-formin 
is  produced,  and  carbonic  anhydride  evolved. 

CiH5(OH),  +  (COOH)tI2H10  = 

311,0  +  C02  +  C3II5(OH)2-  (OCHO). 

(2)  This  mono-tbrmin.  acted  upon  by  fresh  portions  of 
oxalic  acid,  reproduces  the  glycerol,  and  evolves  formic 
acid,  which  distills  over 


Anhydrous  formic  acid  is  a  colorless  volatile  liquid,  of 
pungent  odor,  boiling  at  100°C.  and  solidifying  at  0°C; 
sp.  gr.  1.23.  The  strongest  hydrated  acid  is  CH2O2,  II  2O, 
which  boils  at  100°. 

Formic  acid  may  be  regarded  as  the  half  aldehyde  of 
carbonic  acid,  II  -CO  -OH.  It  reduces  silver  nitrate,  and 
is  itself  oxidized  to  carbonic  acid,  HO  •  CO  •  OH. 

681.  Acetic  acid,  C2H4O2  or  CII3-  COOII,  known  and 
used  from  the  earliest  times  in  some  form  of  vinegar, 
is  a  frequent  product  of  the  oxidation  of  many  organic 
substances.  In  the  old  world  it  is  manufactured  on  the 
large  scale  from  the  crude  product  obtained  in  the  de- 
structive distillation  of  wood  (p.  166).  On  neutralizing 
this  distillate  with  sodium  carbonate,  and  evaporating, 
sodium  acetate  crystallizes  out.  This  is  decomposed  by 
strong  H2SO4,  and  again  submitted  to  distillation.  The 
distillate  is  glacial  acetic  acid  so  called,  because  it  solid- 
ifies at  17°C  to  a  transparent  mass, 

NaC2H802  +  H2S04  =  NaHSO4  +C2H4O2. 


ORGANIC  ACIDS. 


359 


In  this  country  it  is  prepared  from  dilute  alcohol 
which  is  suffered  to  trickle  slowly  over  bard  wood  shav- 
ings, contained  in  a  large  cask,  through  which  the  air  is 
made  to  circulate  freely.  (Fig.  104.)  At  the  start,  a 
little  yeast  or  old  vinegar  is  added  to  sow  its  ferment, 
the  mycodcrma  aceti.'  A  temperature  of  about  30°C  is 
maintained,  and  the  process  is  completed  in  a  few  days. 

The  best  vinegar  is  that 
obtained  from  the  natural 
souring  of  cider  and  wine. 
It  contains  from  3  to  15 
per  cent  of  the  glacial  acid. 
It  has  a  well  known  odor 
and  a  pleasant  acid  taste. 

The  glacial  acetic  acid  is 
a  colorless  liquid,  capable 
of  blistering  the  skin;  sp. 
gr.,  1.063 ;  boiling  point, 
118°.  Its  vapor  density  at 
300°  is  30,  being  exactly 
that  required  by  theory. 
Monohydrated  acetic  acid,  FlG  1(M 

C2H4O2,  H2O,  has  a  dens- 
ity of  1.079,  but  with  either  a  greater  or  less  amount  of 
water  the  density  diminishes,  hence  the  specific  gravity 
can  not  be  used  to  determine  the  strength  of  acetic  acid. 
Its  strength  is  ascertained  by  observing  the  quantity  of 
sodium  carbonate  which  is  required  to  neutralize  a  given 
amount  of  the  acid. 

Acetic  acid  forms  a  large  number  of  important  ace- 
tates, either  by  direct  union  with  metallic  oxides  or  by 
decomposition  of  their  carbonates. 

Potassium  acetate,  'KC2H3O2  or  CH3  •  COOK,  is  a 
white  deliquescent  body,  soluble  in  alcohol.  [Exp.  42, 
p.  36.] 

Sodium  acetate,  NaC2H3O2- 3H2O,  crystallizes  in  large 


360  ORGANIC  CHEMISTRY. 

prisms,  which  are  efflorescent,  soluble  in  three  times 
their  weight  of  cold  water. 

Ammonium  acetate  decomposes,  on  heating,  to  water 
and  acetamide,  <'II3-  CO(XNH4  =  II,  O  -f  (!1I3COXH2. 

The  alkalies  also  form  so-called  "acid  salts,"  in  which 
they  take  up  an  additional  molecule  of  the  acid;  thus 
potassium  di  -acetate,  C2II3O0K,  ('2n4O0,  is  formed  when 
the  normal  acetate  is  dissolved  in  strong  acetic  acid  and 
the  mixture  evaporated. 

The  acetates  of  iron,  Fc2(OC2II3O)6,  and  of  alumina, 
Al2(OC2IIaO)ft,  are  easily  decomposed  upon  boiling  their 
solutions  into  basic  salts  and  free  acetic  acid.  They  find 
extensive  employment  as  mordants  in  calico  printing. 

Lead  acetate,  I>1»(()(12H3O)2,  :HI2<>,  sugar  of  lead,  is 
formed  by  dissolving  litharge  in  vinegar.  It  has  a 
sweetish  but  disagreeable  metallic  taste,  and  is  poisonous. 
There  arc  several  basic-  salts  obtained  by  digesting  a 
solution  of  sugar  of  lead  with  lead  oxide.  These  are 
also  formed  in  the  manufacture  of  white  lead,  being  de- 
composed by  carbonic  anhydride  into  free  acetic  acid 
and  the  basic  lead  carbonate.  See  £  422. 

Cupric  acetate,  (1u(O(1.,  II3O)2,  II.,O,  is  moderately  sol- 
uble in  water,  and  is  easily  decomposed  on  boiling  to 
a  basic  acetate.  Yerdiyris  is  a  mixture  of  basic  cupric 
salts  obtained  by  exposing  metallic  copper  to  the  joint 
action  of  the  air  and  vinegar. 

TKSTS.  1.  On  heating  any  dry  metallic  acetate  in  a  hard  glass 
tube,  the  odor  of  acetone  will  be  perceived.  The  vapors  are  in- 
flammable. 

'2.  On  heating  a  mixture  of  a  metallic  acetate  and  sulphuric 
acid  with  alcohol,  acetic  ether  will  be  given  off,  and  may  be  rec- 
ognized by  its  pleasant  odor. 

682.  Propionic  acid,  C8H6O2  =  C2II5-  COOH,  is  ob- 
tained by  boiling  ethyl  cyanide  with  sulphuric  acid, 


C2II5CN-f-2II2O-f  II2S04  =  XH4HS04-fC2II5  COOH. 


ORGANIC  ACIDS.  361 

It  is  separated  from  its  solution  in  water  as  an  oily 
layer  on  the  addition  of  calcium  chloride.  In  other  re- 
spects it  strongly  resembles  acetic  acid. 

683.  Butyric  acid,  C4H8O2  =C8H7- COOH,  has  two 

isomeric  forms  which  closely  resemble  each  other. 

Normal  butyric  acid  is  found  either  free  or  combined 
in  the  juices  of  many  plants  and  animals,  and  is  a  fre- 
quent product  of  fermentation.  The  best  method  of  pre- 
paring it  is  by  the  fermentation  of  sugar  in  contact  with 
putrefying  cheese.  Lactic  acid  is  first  formed, 


and  is  removed  by  the  addition  of  chalk,  as  calcium  lac- 
tate.  After  a  time,  this  calcium  lactate  undergoes  a 
second  fermentation  to  calcium  butyrate,  2C3H6O3  = 
C4H8O2  -f-  H2  -|-2CO2.  The  peculiar  offensive  odors  of 
rancid  butter,  limburger  cheese,  saner  kraut,  etc.,  are 
due  partly  to  butyric  and  lactic  acids,  and  partly  to  the 
volatile  acids  with  which  they  are  usually  associated, — 
valeric,  caproic,  caprylic,  capric. 

Iso  butyric  acid,  (CH3)2,  CH- COOH,  is  found  in  St. 
John's  bread,  but  is  prepared  by  oxidation  of  the  iso- 
butyl  alcohol  obtained  from  fusel-oil. 

684.  Four  isomeric  forms  of  valeric  acid  have  been 
prepared : 

Propyl  acetic  (normal),  CH3-  CH2-  CH2-  CH2-  COOH. 

Isopropyl  acetic,  (CH3)2,  CH  •  CH2-  COOH. 

Methyl  ethyl  acetic,  CH3,  C2H5  •  CH  •  COOH,  or 
CH3,  (CH3  •  CH2)  •  CH  •  COOH. 

Tri-methyl  acetic,  (CH3)3  :    C  •  COOH. 

The  second  of  these  is  the  ordinary  "valerianic"  acid. 
It  occurs  free  in  the  valerian  root  to  which  it  gives  its 
characteristic  odor.  It  is  now  prepared  by  the  oxidation 
of  isoamyl  alcohol.  Some  of  the  salts  are  used  in  med- 
icine, as  nervous  sedatives. 


362  ORGANIC  CHEMISTRY. 

The  isomerx  possible  in  the  higher  members  rapidly 
increase,  but  after  C12  few  isomers  are  known. 

685.  Palmitic  acid,  C16II32O2  =  C11TI31- ('OOTI,  and 
Stearic  acid,      C18II36O2  =  C,  7II35- COOIT, 

are  the  most  important  of  the  non-volatile  acids  of  this 
series,  being  found  as  palmitin  and  stearin  in  most  solid 
fats  and  fixed  oils.  In  their  crude  state,  they  are  the 
principal  constituents  of  '•  stearin  candles/'  obtained  by 
the  saponitication  of  lard  and  tallow.  When  purified 
from  their  alcoholic  solutions,  they  crystallize  in  shining 
plates  that  melt,  palmitic  at  (Yl°(\  stearic  at  t>9°. 

686.  The  acrylic  series  of  acids, 

<'jr,.«-A,  or  C,,,!!,,,,., COO II, 

contains  upwards  of  twenty  known  acids  which  may 
be  regarded  as  derived  from  ethylene  and  its  homo- 
logues.  The  series  takes  its  name  from  its  lowest  mem- 
ber, acrylic  acid,  C2II3-  COOII,  which  is  produced  by 
the  oxidation  of  acrolcin  (p.  331).  These  acids  are  con- 
verted to  the  corresponding  fatty  acid  by  nascent  hy- 
drogen, acrylic  becoming  propionic  acid, 

C2JI3- COOII  4-II2       C2 II,   COOII, 

and  into  two  fatty  acids  by  fusion  with  caustic  potash, 
acrylic  acid  yielding  potassium  formate  and  acetate, 

C21I3-  COOII  +  2KOH  =  CII3- COOK  +  II  •  COOK  +  fl2. 

Many  of  these  acids  are  oily  bodies  which  are  found 
as  glycerides  accompanying  those  of  the  fatty  acids.  Of 
these  acids  the  most  important  is: 

Oleic  acid,  C18II34O2  =  C,  7H33  COOII.  It  is  found 
as  olein  in  nearly  all  soft  fats,  like  lard,  and  is  the  chief 
constituent  of  such  fixed  oils  as  olive,  almond,  cotton- 
seed, etc.  Free  nitrous  acid  converts  it  to  a  solid  iso- 


ORGANIC  ACIDS.  363 

mer,  elaidic  acid.     This  reaction  serves  also  as  a  test  for 
the  presence  of  oleic  acid  in  oils. 

Fuming  nitric  acid  oxidizes  it  with  violence,  producing 
a  great  variety  of  products,  including  nearly  all  of  the 
volatile  fatty  acids,  and  those  of  the  oxalic  series.  Olive- 
oil  and  other  oils  which  contain  olein,  oxidize  slowly  in 
the  air,  probably  giving  rise  to  the  same  volatile  acids 
which  contribute  to  the  odor  and  taste  of  the  rancid  fats. 
Very  recently  it  has  been  found  profitable  in  the  manu- 
facture of  candles  to  convert  oleic  into  palmitic  acid  by 
treatment  with  KOII. 

687.  The  natural  fats  and  fixed  oils  are,  almost  without 
exception,  mixtures  of  several  glycerides  of  the  mono- 
basic acids.  Palmitin,  stearin,  and  ole'in  are  nearly  al- 
ways found ;  and  the  character  of  a  fat  is  largely  depend- 
ent on  the  proportion  in  which  it  contains  these  three: 
the  solid  fats,  as  mutton-suet,  are  principally  tri-stearin 
(C3H5)  I  O3  :  (C18H85O)8;  the  fluids,  like  olive-oil, 
mainly  tri-olein,  (C3H.)  j  O3  |  (C18H33O)3;  palm-oil  is 
chiefly  tri-palmitin  (C3H5)  .:  O3  \  (C16H31O)3.  Some 
fats,  as  cocoa-nut  oil,  castor-oil,  and  the  various  butters, 
contain  nearly  all  the  fatty  acids  of  an  even  number 
of  carbon  atoms  from  C4  to  C22  inclusive. 

These  oils  are  called  fixed  to  distinguish  them  from  the  fragrant 
volatile  or  essential  oils,  lemon,  wintergreen,  etc..  which  contain  no 
glycerol.  They  may  be  recognized  by  giving  off  the  pungent  va- 
pors of  acrolei'n  when  thrown  upon  a  heated  stove-plate,  and  by 
their  leaving  a  permanent  grease  spot  when  smeared  upon  paper. 
They  are  generally  insoluble  in  water  and  alcohol,  but  are  readily 
soluble  in  ether  and  carbon  bisulphide.  All  float  upon  water, 
and  are  fluids  above  100°C.  Subjected  to  cold  they  undergo  a 
partial  separation;  thus,  the  solid  fat  which  separates  out  from 
olive-oil  in  the  cold  of  winter  is  nearly  pure  palmitin. 

In  their  pure  state  most  of  these  bodies  are  colorless,  odorless, 
and  tasteless;  but,  as  usually  prepared,  they  contain  foreign  mat- 
ters which  impart  a  characteristic  flavor  and  odor;  thus,  the  odor 
of  fish-oils  is  frequently  due  to  the  presence  of  valeric  acid.  When 


364  ORGANIC  CHEMISTRY. 

fattv  bodies  are  exposed  to  the  air,  the  albuminous  matters  they 
contain  putrefy,  and  induce  a  sort  of  fermentation  by  which  the 
oils  become  rancid,  liberating,  or  perhaps  forming,  the  volatile  acids, 
capric,  valeric,  butyric,  etc. 

Castor-oil  contains  ricinoleic  acid,  C18II34O3,  in  place  of  oleic 
acid.  It  may  be  made  to  yield  octylic  alcohol  and  pelargonic 
acid,  and  is  one  of  the  few  fixed  oils  which  are  soluble  in  alco- 
hol. It  is  extensively  employed,  not  only  in  medicine,  but  in  the 
arts. 

The  drying  oils  are  so  called  because  they  do  not  emit  rancid 
odors  on  oxidation,  but  harden  to  a  varnish-like  mass.  This  prop- 
erty is  increased  by  boiling  them  with  *\jth  their  weight  of  litharge. 
They  contain  linoleic  acid,  C,fiII2SO2.  The  principal  drying  oils 
arc  linseed,  hemp,  and  poppy.  They  arc  used  in  the  manufacture 
of  oil  varnishes  from  copal  and  other  resins,  and,  when  mixed  with 
white  lead,  zinc,  etc.,  constitute  the  ordinary  oil  paints. 

688.  The  separation  of  the  acids,  which  are  contained 
in  the  oils,  is  attended  with  special  difficulties. 

(1)  The  oils  are  first  saponified  and  the  glycerine  removed.     The 
usual    process  is   by  means  of  superheated  steam,  but  sometimes  a 
small   proportion  of  lime  or  of  sulphuric  acid   is  first  added. 

(2)  Most  of    the  oleic   acid   is   removed    by   pressure,   the  residue 
warmed  and   again  compressed.     The  hard  cake  remaining  is   used 
in  the  manufacture  of  stearin  candles. 

(3)  From   such  crude  materials  the  volatile  acids  are  separated 
by  "partial  saturation,"  followed  by  "fractional  distillation."     Half 
tla>   crude    mass    is    neutralized    by   an    alkali,    then    added    to    the 
other   portion    and   subjected    to    distillation.     Naturally,  the    acid 
which  has  the  lower  boiling  point  will  pass  over  first.     If  sufficient 
alkali   has  been   added    to  saturate  the  higher  carbon  acid,  nearly 
all  of  the  distillate  will  consist  of  the  volatile  acids.     By  repeating 
this  process,  the  lowest  carbon  acid  will  be  obtained  pure. 

The  separation  of  the  higher  fatty  acids  is  effected  by  "fractional 
precipitation;"  e.  g.,  suppose  a  mixture  of  palmitic  and  stearic 
acids.  (1)  It  is  dissolved  in  alcohol  and  about  i  precipitated  by 
magnesium  acetate.  This  first  seventh  consists  principally  of  the 
higher  carbon  acid  (stearic).  (2)  The  magnesian  salt  is  decom- 
posed by  hydrochloric  acid,  the  fatty  acids  washed  and  again  dis- 
solved in  alcohol.  (3)  }  part  (now  Jg)  is  again  precipitated,  and 
the  process  repeated  until  two  successive  products  exhibit  identical 


ORGANIC  ACIDS.  365 

boiling  points,  specific  gravities,  etc.  Pleintz  repeated  these  opera- 
tions 33  times  before  obtaining  pure  stearic  acid. 

689.  Soaps  arc  the  metallic  salts  of  the  higher  carbon 
acids,  palmitic,  oleic,  etc,  The  alkaline  soaps  only  are 
soluble  in  water;  the  hard  soaps  contain  soda,  the  soft, 
soaps  potash.  These  soaps,  when  added  to  much  water, 
suffer  a  partial  dissociation  into  a  basic  salt  and  a  free 
alkali.  The  free  alkali  works  cleansing  upon  the  greasy 
articles  submitted  to  its  action,  the  basic  salt  forms  the 
lather  and  assists  in  removing  dirt  by  its  mechanical 
action. 

Usually,  in  preparing  soft  soaps,  the  crude  fats  are 
boiled  with  potash  lye,  glycerol  is  set  free  and  passes 
into  solution,  together  with  the  soap  which  is  formed ; 

e.  g.,  C3H5  ;03  ;  3C18II850  +  3KOH  = 

C8H6(OH)8  +  3KC18H8502. 

These  products  are  boiled  down  to  a  thick  mass,  and 
usually  contain  an  excess  of  alkali.  The  "glycerine  soda 
soaps "  are  made  by  heating  a  similar  mixture  of  fat 
and  soda  lye,  to  expel  most  of  the  water,  and  run  into 
moulds;  the  glycerol  remains  mixed  with  the  soap. 

Ordinarily,  the  hard  soaps  are  made  by  adding  to 
either  of  these  two  crude  soaps,  while  still  in  solution,  a 
quantity  of  common  salt.  A  soda  soap  at  once  separates 
out  and  rises  to  the  top  of  the  boiler's  vat.  It  is  drawn 
off  into  movable  frames,  in  which  it  hardens  sufficiently 
to  be  cut  into  bars.  A  portion  of  the  acids  used  for  the 
cheap  bar  soap  is  obtained  from  common  resin.  Castile 
soap  is  made  from  olive  oil.  The  mottling  which  some 
varieties  exhibit  is  due  to  the  presence  of  iron  oxide. 

It  is  said  that  mottled  soaps  do  not  contain  more  than 
30%  of  water.  Some  soaps  contain  as  much  as  70%  of 
water.  Cocoa-nut  oil  and  soluble  glass  are  added  to 
soaps  for  the  purpose  of  absorbing  H2O,  and  thereby 
increasing  the  weight. 


366  ORGANIC   CHEMISTRY. 

Transparent  soaps  are  produced  by  dissolving  a  dried 
soda  soap  in  alcohol,  distilling  off  the  alcohol,  and  run- 
ning the  melted  mass  into  moulds. 

The  soluble  salts  of  lime,  magnesia,  and  other  dyad 
metals,  when  added  to  solutions  of  the  alkaline  soaps, 
immediately  decompose  them,  and  produce  soaps  which 
are  insoluble  in  water  and  worthless  for  purposes  of 
washing;  as, 


SECOND  GROUP — DIHYDRIC  ACIDS. 

690.  The    primary    glycols    yield    on    oxidation    acids 
which    contain    two    hydroxyl    groups    (p.    332).      These 
acids   fall    into  two  series:    (1)  The  monobasic  or  lactic 
series,  which  contain   but    one   COOH    radical.     (2)  The 
bibasic  or  oxalic  series,  which  contain  two  (JOOH  groups. 

691.  The  monobasic  may  be  derived  also  from  the  fatty 
acids  by 'substitution  of  Oil  for  II   in  the    alkyl    radical. 
This  is  effected  by  first  forming   the  mono-chlor  deriva- 
tive of  the  fatty  acid,  and  then  acting  upon  this  product 
with  moist  silver  oxide.     When  treated  in  this  manner, 
propionic  acid  is  converted  to  lactic  acid. 

(1)  CH3-  CH2-  COOII  -f  C12  =  ITC1  +  CH3  CHC1  COOH. 

(2)  CH8-CHC1   COOH-fAgHO  = 

AgCl  -f  CH3  CHOII  •  COOH. 

The  usual  names  of  these  bodies  are  formed  by  prefixing 
uoxy"  to  those  of  the  fatty  acids.  Three  have  received 
special  names, — glycollic  or  oxy-acetic,  lactic  or  oxy-pro- 
pionic,  leucic  or  oxy-caproic  acid.  Half  a  dozen  have 
been  described.  They  resemble  the  fatty  acids  in  their 
general  reactions,  and  like  them  form  only  one  series  of 
metallic  salts  ;  but  unlike  them  form  three  ethers^with 


ORGANIC  ACIDS.  367 

the  same  alcohol  radical,  one  acid  and  two  neutral.     The 
ethyl  lactic  ethers  are: 


CHS  CH3  CH.  CEL 

I  !  I 

CHOH  CHOC-  II  5  CHOH  CIIOC.H,. 

I  I 

COOH  COOII  COOC2II5  COOC2H5. 

Lactic  Ethyl-lactic  Mon-ethylic  Di-ethylic 

acid.  acid.                            lactate.  lactate. 

Carbonic  acid,  CO(OH)2,  is  theoretically  the  first  member  of  this 
series;  but,  as  either  of  its  hydroxyl  groups  may  enter  into  the 
carboxyl  radical,  OH  •  CO  •  OH,  the  acid  is  di-basic,  and  forms  two 
series  of  metallic  salts. 

Several  acids  of  this  series  are  interesting  because  of  their  close 
relations  to  bodies  found  among  the  products  of  animal  life. 

692.  Glycollic    acid,    CH2OH  •  COOII,    is    frequently 
found   among   the   products  of  the  decomposition  of  or- 
ganic substances.     It  derives  its  name  from  glycocoll  or 
glycocine,  fr%n  which  it  was  first  obtained,  but  glycocine 
may  be  obtained  from  gelatine,  and  is  itself  amido-acetic 
acid,  CII2NH2-  COOH.     Glycollic  acid  may  also  be  pre- 
pared from  glycol  by  partial  oxidation,  but  more  advan- 
tageously by  carefully  oxidizing  ethyl  alcohol  with  nitric 
acid. 

Leucic  acid,  C4H9-  CHOH  COOH,  is  similarly  related 
to  leucine,  which  is  amido-caproic  acid,  a  substance  found 
in  various  organs  of  animals  (brain,  liver,  pancreas). 

693.  Two  lactic  acids  only  are  required  by  theory,  but 
four  acids  are  known  of  the  formula,  C3H6O3. 

(1)  The  ordinary  lactic  acid,  which  is  produced  in 
large  quantities  by  the  fermentation  of  milk-sugar  in 
presence  of  putrefying  cheese,  is  ethylidene  lactic  acid, 
CH3-  CHOH-  COOH.  It  is  found  free  in  the  gastric 
juice.  It  forms  a  syrupy,  sour  liquid;  sp.  gr.,  1.25; 
miscible  with  water  and  alcohol.  On  being  heated,  two 


368  ORGASIC  CHEMISTRY, 

molecules  gradually  lose  water,  becoming  at  last  lactic 
anhydride,  C81I4O0,  which  is  known  as  lactide.  This 
lactic  acid  is  optically  inactive. 

But  (2),  there  exists  in  the  juice  of  flesh  (Liebig's  ex- 
tract) para  lactic  acid,  which  turns  the  plane  of  polar- 
ized light  to  the  left.  These  two  acids  are  otherwise 
strikingly  alike,  and  are  physical  isomers.  They  yield 
identical  products  upon  being  decomposed  by  chromic 
mixture,  producing  formic  and  acetic  acids. 

(3)  Ethylene  lactic  acid,  CII2OH  •  CH2- TOOII  is  also 
found  in  small  quantities  in  flesh  extract,  and  has  been 
prepared     synthetically    from     its    cyanide.      When    the 
flesh  extract  is  oxidized,  malonic  acid   is  formed, 

<'II2OH-CII2  COOII-f  02=,1I2()-|-('<)<)H  CH,-COOH. 

(4)  Hydracrylic   acid   may   be  obtained    in    crystalline 
plates  from  glyceric  and   from  acrylic  acids  by  successive 
treatment  with    III    and  AgllO.     On  oxidation   it   yields 
oxalic  and  carbonic  acids. 

The  zinc  salts  of  these  isomeric  acids  show  considerable  differ- 
ences in  solubility.  This  property  is  used  to  separate  them  from 
their  mixed  solutions. 

694.  The  oxalic  series  of  bibasic  acids,  C,,H,M(COOII)2, 

contains  about  a  dozen  members.  The  lower  carbon 
acids  may  be  obtained  by  the  complete  oxidation  of  the 
corresponding  glycols ;  the  higher  members  are  gener- 
ally prepared  by  oxidizing  fatty  and  resinous  bodies 
with  nitric  acid.  They  are  for  the  most  part  non-vol- 
atile solids,  crystallizable,  and  soluble  in  water.  They 
form  both  acid  and  neutral  salts  and  ethers  ;  as, 


COOH 

i 

COOH 

i 

COOH 

1 

COOK 

COOC2H5. 

1 

COOH 

COOK 

COOC2H5      COOK 

COOC2H5. 

Oxalic 

Acid 

Ethyl 

Normal 

Ethyl 

acid 

potassium 

oxalic 

potassium 

oxalate. 

oxalate. 

acid. 

oxalate. 

ORGANIC  ACIDS.  369 

695.  Oxalic  acid,  (COOH)2,  is  widely  distributed  in 
plants,  especially  in  the  sorrel  and  rhubarb,  as  calcium 
oxalate.  It  is  also  found  in  urinary  calculi  as  a  calcium 
salt.  It  is  produced  by  the  oxidation  of  a  large  number 
organic  substances,  and  may  be  prepared  by  heating  su- 
gar, starch,  cellulose,  etc.,  with  five  times  their  weight  of 
strong  nitric  acid, 

2C6H1005-{-9(II20-N205)  = 

6C204H2  -f  9No7);  +  13H20. 

On  the  large  scale  it  is  manufactured  by  heating  a  mix- 
ture of  saw-dust  and  caustic  soda.  The  sodium  oxalate 
which  forms  is  decomposed  by  boiling  with  slaked  lime, 
and  the  resulting  calcium  oxalate  by  means  of  sulphuric 
acid. 

Oxalic  acid  dissolves  in  less  than  its  own  weight  of 
boiling  water.  On  cooling,  the  greater  part  crystallizes 
out  in  prisms,  C2O4H2,  2H2O.  If  this  acid  be  carefully 
heated,  (1)  it  loses  its  water  of  crystallization  at  100°C; 
(2)  the  remaining  anhydrous  acid  sublimes  undecom- 
posed  at  150°C,  but  (3),  if  rapidly  heated  to  higher 
temperatures,  is  completely  broken  up, 

2C204H2  =  H20  -f  2(X)2  -f  CO  -f-  H  •  COOII. 

Similar  decompositions  are  effected  by  most  dehydrating 
agents,  yielding  among  other  products  carbonous  oxide 
and  formic  acid.  Oxalic  acid  is,  therefore,  a  strong  re- 
ducing agent ;  its  solutions  reduce  salts  of  the  noble 
metals. 

Exp.  198. — Repeat  Exp.  196,  page  268,  using  oxalic  acid  in 
place  of  ferrous  sulphate.  Add  H2SO4.  Notice  the  different  ra- 
pidity with  which  the  permanganate  is  bleached  when  poured  into 
a  warm  or  a  cold  solution  of  oxalic  acid. 

Oxalic  acid   forms  with   most   of  the   dyad   metals   only  normal 

salts;   as,  C2O4Ca,  4H2O.     With  monovalent  metals,  as  potassium, 

normal  salts;   as,  02O4K2,  2H2O,  acid  salts;   as,  C2O4HK,  2H2O, 

and  also   hyper-acid,  C2O4HK,  C204H2,  2H2O.     The  solutions  of 

Chem.— 24. 


370  ORGANIC  CHEMISTRY. 

the  normal  alkaline  oxalates  are  neutral  to  litmus,  and  hence  ox- 
alic acid  is  employed  in  .  hi  metric  analyses  of  alkalies. 

All  the  oxalates  are  decomposed  by  heat  without  separation  of 
carbon,  (1)  evolving  CO  and  leaving  metallic  carbonates,  as  those 
of  the  alkalies;  (2)  those  carbonates  which  are  also  decomposed  by 
heat  (Zn,  Mg,  Ca),  leaving,  when  strongly  heated,  only  metallic 
oxides;  as,  ZnO;  (3)  evolving  CO2,  and  leaving  only  the  metals. 
The  last  reaction  affords  a  method  for  obtaining  pure  metallic 
cobalt  and  other  metals. 

The  alkaline  oxalates  are  soluble  in  water,  the  other  oxalates 
(except  Fe)  are  nearly  insoluble  in  water,  but  are  readily  soluble 
in  solutions  which  contain  free  mineral  acids.  Calcium  oxalate  is, 
however,  not  soluble  in  excess  of  oxalic  or  acetic  acids,  and  hence 
CaCl2  is  a  delicate  test  for  the  presence  of  oxalic  acid  in  solutions 
containing  no  acids  except  these. 

Oxalic  acid  and  its  soluble  salts  are  used  in  calico  printing,  in 
the  manufacture  of  blue  ink,  and  in  bleaching  straw  goods,  also 
for  cleansing  brass,  and  for  taking  iron  mould  out  of  cloth.  The 
acid  potassium  oxalate,  which  is  used  for  the  last  purpose,  is  sold 
under  the  names  of  "salt  of  sorrel"  and  ''salt  of  lemons."  It  is 
sometimes  used  in  making  the  cheap  "lemonade"  at  fairs,  etc. 

Oxalic  acid  and  its  soluble  salts  are  highly  poisonous.  The 
proper  antidote  is  precipitated  chalk  or  whiting. 

696.  Malonic  acid,  COOII    OH2  COOH,  may  be  ob- 
tained from  monochloracetic  acid  by  (1)  boiling  this  with 
potassium    cyanide,   and    (2)    by   heating   the    cyanacetic 
acid   thus   produced   with    an   alkali.     It  and   its  ketonic 
derivative,  mesoxalic  acid,  COOH -CO- COOH,  are  chiefly 
interesting  because  of  their  relations  to  lactic  and  malic 
acids,  and  to  the  compound  ureas. 

697.  Succinic  acid   has   two   modifications.     The  ordi- 
nary succinic  acid,  COOH  •  (CH2)2-  COOH,  occurs  ready 
formed   in   amber  and   in   many  plants.     It  is   obtained 
by  the  dry  distillation  of  amber  (yield  4%),  and  is  one 
of  the    products   of  the    long-continued   action   of  nitric 
acid    upon   the   fats.     It   is  advantageously  prepared   by 
the  fermentation  of  calcium  malate  or  tartrate  with  old 
cheese.     The  calcium  succinate  which  results  is  decom- 


ORGANIC  ACIDS.  371 

posed  by  sulphuric  acid.  The  succinic  acid  remains  in 
solution,  and  -is  purified  by  recrystallization  and  by  sub- 
limation. It  forms  colorless  prisms  which  melt  at  180°C 
and  boil  at  235°,  undergoing  decomposition  into  water, 
and  succinic  anhydride  (CII2-CO)2O,  which  distill  over. 
The  anhydride,  on  long  boiling  with  water,  is  recon- 
verted into  the  acid.  Ammonium  succinate,  when  boiled 
with  neutral  aluminium  and  ferric  solutions,  completely 
precipitates  these  metals  as  basic  succinates. 

698.  Three   other  series   of  bibasic   acids  are   known, 
each  of  which  contains  from  three  to  ten  members: 

Fumaric  series,  CnlI2n_2(COOH)2. 
Malic  series.        CJI^OII,  (COOH)2. 
Tartaric  series,  CrtH2n_2(OH)2,  (COOH)2. 

Besides  tbese  there  are  a  few  tribasic  acids,  as  citric 
acid,  CnH2n_2(OH)(COOH)3,  as  well  as  a  number  of 
higher  basicity,  which  have  not  as  yet  been  arranged  in 
series. 

699.  Fumaric  and  maleic  acids,  C4H4O4,  are  isomers 
produced  by  the  dry  distillation  of  malic  acid, 


and  are  converted  by  nascent  hydrogen,  H2,  into  suc- 
cinic acid,  C4II6O4.  Fumaric  acid  also  occurs  in  the 
free  state  in  various  plants,  as  in  Iceland  moss. 

700.  Oxalic,  malic,  tartaric,  and  citric  acids  are  gen- 
erally associated  together  by  twos  and  threes  in  the  sour 
juices   which    exist   in  the   stalks,   leaves,   and   fruits  of 
plants,  sometimes  in  the  free  state,  but  more  frequently 
in    combination   with    calcium   or   potassium.     They   are 
the   chief  sources   of  the   potassium   carbonate  which   is 
found  in  the  ashes  of  plants. 

701.  Malic  acid,  C4H6O5=COOH  •  CHOH  •  CH2-  COOH, 
is  found  in  many  sour  fruits  (unripe  apples,  gooseberries, 


372  ORGANIC  CHEMISTRY. 

etc.,)  but  is  especially  abundant  in  the  nearly  ripened 
berries  of  the  mountain  ash  and  of  the  sumach.  It  may 
also  be  prepared  advantageously  from  the  expressed  juice 
of  any  one  of  these,  also  artificially  by  the  reduction  of 
tartaric  acid,  and  by  the  oxidation  of  succinic  acid.  The 
latter  process  yields  an  acid  optically  inactive;  the  ordi- 
nary malic,  acid  rotates  polarized  light  to  the  left.  The 
malic  acids  are  white  deliquescent  bodies,  soluble  in  al- 
cohol, and  of  an  agreeable  acid  taste.  They  arc  easily 
reduced  to  succinic,  butyric,  and  acetic  acids. 

702.  Asparagin  is  a  crystallizablo  substance  present  in 
asparagus,  and  in  the  young  shoots  of  many  plants.     On 
boiling  it  with  acids  or  with  alkalies,  it  becomes  aspartic 
acid,  but    if  either  asparagin  or  aspartic  acid    is  treated 
with    nitrous   acid,  malic  acid    is    produced.     These   are, 
therefore,  amide   l>odies.      Any  one  of  these  three,  when 
fermented  with  old  cheese,  yields  succinic  acid,  and  this 
in   turn    butyric  acid,  etc.     These  relations  are  supposed 
to  play  an  important  role  in  the   growth  of  plants,  and 
are  partially  exhibited  by  their  structural  formula1: 

Asparagin,         COOII  •  CIIXII2-  CII2-  COXH2. 
Aspartic  acid,  COOII  •  CHNH2- CH2- COOII. 
Malic  acid,         COOII  •  CHOH  •  CII2-  COOII. 
Succinic  acid,    COOII  •  CII2- C1I2- COOII, 

703.  Tartaric  acid, 

C4II606  =  COOH  -  CHOH  •  CHOH  •  COOH 

occurs  especially  in  the  grape.  It  is  manufactured  from 
the  crude  acid  potassium  tartrate  or  argol,  which  is  de- 
posited in  red  crusts  during  the  ripening  of  wines.  This 
salt,  which  requires  240  parts  of  cold  water  for  its  solu- 
tion, dissolves  in  14  parts  of  boiling  water.  It  is  purified 
by  dissolving  in  boiling  water  containing  animal  char- 
coal, filtered  and  recrystallized.  It  is  sold  under  the 
name  of  cream  of  tartar,  and  is  largely  used  in  baking 


ORGANIC  ACIDS.  373 

powders.      The    normal    salt,   K2C4H4O6,   is   soluble   in 
less  than  half  its  weight  of  cold  water. 

The  acid  is  prepared  by  boiling  the  purified  cream  of 
tartar  with  powdered  chalk,  first  producing  insoluble  cal- 
cium tartrate  and  normal  Dotassium  tartrate. 


2KIIC4II406  -f 

II20  +  C02  +  CaC4_lI40_6  +  K2C4H406. 

Calcium  chloride  is  now  added  to  decompose  the  latter, 
and  the  calcium  tartrates  are  digested  with  dilute  sul- 
phuric acid.  CaC4H4O6-fH2SO4=CaSq4+H2C4H406. 
The  tartaric  acid  is  filtered  off  from  the  insoluble  calcium 
sulphate,  and  on  evaporation  crystallizes  in  large  mono- 
clinic  prisms,  easily  soluble  in  water.  On  heating  to 
135°C  it  is  changed  to  its  isomer,  metatartaric  acid,  an 
uncrystallizable  gum-like  mass.  At  150°  it  loses  water, 
and  changes  to  its  anhydride,  C4H4O5,  and  at  higher 
temperatures  undergoes  decomposition,  yielding  a  great 
number  of  products,  among  which  are  pyrotartaric,  acetic, 
and  formic  acids,  and  evolving  a  characteristic  odor  of 
burnt  sugar.  Tartaric  acid  is  readily  oxidized,  yielding 
in  most  cases  formic  acid,  and  hence  acts  reducing  on 
the  noble  metals. 

Exp.  199.—  Add  to  a  neutral  solution  of  silver  nitrate  a  solu- 
tion of  neutral  ammonium  tartrate,  and  dissolve  this  in  ammonia, 
avoiding  excess.  Now  heat  a  portion  of  this  solution,  diluted,  if 
necessary,  in  a  perfectly  clean  test-tube  to  a  temperature  nearly, 
but  not  quite,  its  boiling  point  for  some  time.  Metallic  silver  will 
separate  out  and  form  a  brilliant  mirror  on  the  glass. 

704.  The  normal  tartrates  of  the  alkalies  and  Eochelle 
Salt,  KNaC4H4O6,  4H2O,  are  easily  soluble;  the  acid 
tartrates  (except  Na),  but  sparingly  (p.  207).  Heated, 
they  first  blacken,  but  in  free  air  the  fixed  alkaline  tar- 
trates at  last  burn  to  pure  white  carbonates. 


374 


ORGANIC  CHEMISTRY. 


Tartar  emetic,  KvSbOC4H4O6,  is  made  by  boiling  cream  of  tar- 
tar with  antimonous  oxide,  #209.  It  is  poisonous.  Tartaric  acid 
and  its  soluble  salts  are  used  in  calico  printing,  in  tinning  pins, 
in  baking  powders,  and  in  medicine. 

705.  There  are  four  physical  isomers  of  tartarie  acid, 
which  are  identical  in  chemical  properties  with  the  ordi- 
nary acid. 

1.  Dextro-tartaric  acid,  so  called   because   its  aqueous 
solution  turns  the  piano  of  polarized  light  to  the  right. 

2.  Lsevo-tartaric  acid  turns  the  plane  of  polarization  to 
the  left. 

3.  Racemic  acid,  which  is  optically  inactive,  but  which 
may  be  resolved  into  the  two  former. 

4.  Inactive  tartarie  acid,  which  has  no  effect  on  polar- 
ized light,  but  which  can  not  be  so  separated. 

When  Dextro  tartaric  acid  is  heated  with  a  little  water  to  175° 
under  pressure,  it  is  converted  into  a  mixture  of  two  inactive 
acids.  On  evaporation,  racemic  acid  crystallizes  out  first,  the  in- 
active acid  remaining  in  solution  may  be  entirely  converted  to  ra- 
cemic acid  by  long  boiling. 

If  equal  quantities  of  racemic  acid  are  saturated  with  soda  and 
ammonia  separately,  crystals  are  obtained  which  are  identical  in 
form,  but  if  the  two  solutions  are  mixed  a  double  salt, 

NaNII4C4H4Ot;,  4II2O, 

is  formed,  which,  on  evaporation,  yields  two  crops  of  rhombic  crys- 
tals exactly  alike, 
except  that  the 
hemihedral  faces, 
h,h,  of  one  are 
turned  to  the  right, 
and  those  of  the 
other  to  the  left, 
so  that  one  is  a  sort 
of  reflected  image 
of  the  other.  If 

the  two  kinds  of  crystals  are  separated  and  dissolved  in  water, 
they  will  each  deflect  a  polarized  ray  of  light  to  the  same  extent, 
but  in  opposite  directions ;  that  is,  one  now  contains  dextro-tartaric 


FIG.  105. 


RECAPITULATION.  375 

acid,  and  the  other  laevo-tartaric  acid,  each  of  which  may  be  ob- 
tained in  the  free  state  by  first  precipitating  them  by  CaCl2,  and 
subsequently  decomposing  the  salt  with  H2SO4.  Moreover,  if  equal 
amounts  of  dextro  and  laevo-tartaric  acids  be  mixed  together  in  so- 
lution, racemic  acid  will  be  produced,  with  elevation  in  tempera- 
ture, showing  a  combination  has  taken  place. 

706.  Citric  acid,  C6H8O7  =  (C3H4OH)(COOH)3,  oc- 
curs free  in  lemons  (5J%),  currants,  and  other  acid  fruits. 
It  is  prepared  from  lemons  (1)  by  boiling  the  juice  to 
remove  albuminous  matters;  (2)  saturating  the  clarified 
liquid  while  hot  with  calcium  carbonate;  and,  (3)  finally, 
decomposing  the  calcium  citrate  with  sulphuric  acid. 
The  filtered  solution  yields,  on  evaporation,  colorless 
prisms,  which  melt  at  100°C,  and  become  anhydrous; 
heated  above  175°C,  aconitic  acid,  C6H6O6,  identical 
with  that  obtained  directly  from  monkshood;  and  at 
higher  temperatures,  other  products.  Citric  acid  forms 
three  series  of  salts,  those  of  potassium  having  the  com- 
position: (Normal)  K3C6H5O7,  II2O, 
(Di-potassic)  K2HC6H5O7, 
(Monopotassic)  KH2C6H5O72H2O. 

Tartaric  and  citric  acids  are  used  in  dyeing  and  in  calico  print- 
ing, and  their  salts  are  used  in  medicinal  preparations.  Solutions 
of  ammonium  citrate  are  used  in  the  analyses  of  fertilizers  as 
solvents  for  the  so-called  "reverted  phosphates." 


Recapitulation. 

(1)  All  acids  contain  H,  replaceable  by  metals;  as,  in  HC1,  HCN, 
H,  C2H302. 

(2)  The   best   known  of   the  organic  acids  contain  the   group  hy- 
droxyl  (OH);  as,  HO  •  C2H3O. 

(3)  This  hydroxyl  may  be  contained  not  only  in  the  acid  radical 
COOH,  carboxyl,  or  SO2OH,  etc.,  but  it  may  also  be  a  part  of 
the  alcoholic  radical  CHOH,  etc. 


376  ORGANIC  CHEMISTRY. 

(4)  The  hydrogen  of   such   groups  as  COOII,  SO2OII,  are   easily 
replaced   by  metallic  oxides,  but  this  is  not  the  case  with  al- 
cohol radicals  like  CIIOH. 

(5)  Accordingly,  the  words  mono-hydric,  di-hydric,  etc.,  refer  to 
the  number  of  hydroxyl  (Oil)  molecules  present  in  an  acid. 

(6)  Accordingly,  also,  the  words  mono-basic  and  di-basic,  etc.,  re- 
fer to  the  number  of   H  atoms  present  in  an  acid  which  may 
be  replaced  by  metallic  hydroxides,  like  KOH. 

(7)  The  best  known  organic  acids  contain  the  carboxyl  COOII. 

(8)  The  hydroxyl  of  this  group  may  be  replaced  by  Cl,  by  NH2, 
etc.;  as,  CH3     (XX '1. 

(9)  If   hydroxyl   is  supposed   to   be  removed,  an  acid   radical    re- 
mains; as,  C2II3O— -  acetyl. 

(10)  Such   a  group  may  be  united   to  any  other  equivalent  group 
by  linking  oxygen  to  form  acid  anhydrides,  ethereal  salts,  etc. 

(11)  An  acid  which  contains  two  hydroxyl  molecules  or  more  may 
suffer  partial  or  total  displacement  of  its  hydroxyl   by  Cl,  or 
by  NII2,  etc.,  and  thus  give  rise  to  many  different  compounds. 

(12)  The  II  in  the  alkyl  radical  may  be  replaced  by  Cl,  NH2,  etc., 
without  change  in  the  acid  radical  COOII;  as,  CII,C1     COOII. 

(13)  It  is  possible  that  the  II  in  an  organic  acid  may  be  replaced 
(1)   by  positive  atoms,  like  the   metals,  to  form  salts,  such  as 
the  acetates;  (2)  by  negative  radicals,  like  the  haloids,  to  form 
new  acids,  like  the  chlor-acetic  acids;  or  (3),  by  both  of  these 
substitutions;  as  the  chlor-acetates. 

(14)  Very  many  acids  of  high  carbon  percentage  may  be  converted 
into  two  or  more  of  lower  carbon  content  (by  heating  alone 
or  with  KIIO);  as  oleic  to  palmitic. 

(15)  Most  of  these  acids  may  be  arranged  in  series  whose  members 
exhibit   gradational    properties;    as,  the   fatty   acid    series,  the 
lactic  series,  etc. 

X.  B.     Not  a  hundredth  part  of  the  organic  acids  known  have 
been  mentioned  in  this  book. 


CHAPTEE    XXIV. 

AMINES    AND    AMIDES. 

707,  Three  radicals  may  be  obtained   from  ammonia, 
NH3,  which  were   once   termed   amidogcn  (NH2)',  imi- 
dogen   (NH)",  and   nitril   (N)'".      Besides  these,  salts, 
like  NH401,  are  supposed  to  contain  the  imivalent  rad- 
ical ammonium  (NH4)'. 

When  these  radicals  combine  with  positive  radicals, 
AMINES  are  formed;  with  negative  radicals,  AMIDES;  and 
with  both  positive  and  negative,  ALKALAMIDES  (p.  300). 

708.  The  Amines  are  strong  bases,  which  may  be  re- 
garded as  ammonias,  containing  in  place  of  one,  two,  or 
three  atoms  of  hydrogen  in  NH3,  a  like  number  of  alkyi 
radicals.     The  compounds  formed  by  the  successive  re- 
placement of  a   hydrogen  atom  in  the  NH3  group,  are 
termed  primary,  secondary,  and  tertiary;  as,  CH3NH2, 
methyl  amine  (primary);    (CH3)2NH,  di-methyl  amine 
(secondary);  (CH3)3N,  tri-methyl  amine  (tertiary). 

The  prefixes  mono,  di,  tri,  etc.,  denote  the  number  of 
NH3  groups,  which  enter  into  the  new  compound,  arid 
also  indicate  the  number  of  nitrogen  atoms  present ;  as, 
ethene  diamine,  (C2H4)"(]N"H2)2  =  C2H4N2H4. 

There  are  also  compounds  which  are  related  to  both  amines  and 
and  amides,  as  CH2NH2'  CONH2  =  amido  acetamide.  These  am- 
monia derivatives  are  more  widely  distributed  in  plants  and  in 
animals  than  is  usually  supposed.  Doubtless  both  amines  and 
amides  play  an  important  part  in  the  formation  of  the  albumi- 
noids, and  other  organic  compounds  containing  nitrogen,  as  they 

are  always  found  among  the  products  of  their  decomposition.     Most 

(377) 


378  ORGANIC  CHEMISTRY. 

of  the  so-called  active  principles  of  plants,  like  nicotine  and  mor- 
phine, are  amines.  The  amides  are  fitted  by  their  flexible  char- 
acter to  be  of  great  physiological  importance;  they  are  especially 
abundant  in  the  young  shoots  of  plants,  and  in  the  glands  of  ani- 
mals. For  examples,  asparagin,  the  amide  of  malic  acid,  is  fre- 
quently found  in  plants;  and  leucine,  the  amide  of  caproic  acid,  is 
one  of  the  products  of  the  decompositions  of  albuminoid  substances, 
as  is  also  urea,  or  carbamide. 

709.  The  amines  strikingly  resemble  ammonia  in  odor 
and    in    the    alkaline    properties    of   their   solutions,   but 
their  vapors   burn   with    a  continuous   flame    (Exp.   40), 
and   they  arc  stronger  bases  than   ammonia.     Like  am- 
monia,   they   combine   directly    with    the    acids,    forming 
salts  on  the  type  of  the  ammonium  (NIF4)  compounds; 
thus,  ethyl  ammonium  chloride,  C2H5NII301,  is  similar 
in  structure  to  ammonium  chloride,  IINH3C1. 

These  compounds  are  easily  formed  by  heating  in  closed  vessels 
an  alkyl  iodide  with  an  alcoholic  solution  of  ammonia.  For  ex- 
ample, ethyl  iodide  and  ammonia  yield  chiefly  ethyl  ammonium 
iodide,  C2II5I  -f-  NII3  =  C2H5NII3I.  In  practice  several  amines 
are  formed  at  the  same  time.  For  example: 

C2H8NH3I,  ethyl-ammonium  iodide  (primary). 
(C2II5)2NII2I,  di-ethyl  ammonium  iodide  (secondary). 
(C2II5)3NIII,  tri-ethyl  ammonium  iodide  (tertiary). 
(C2H5)4NI,  tetrethyl  ammonium  iodide. 

This  is  probably  due  to  a  progressive  action,  whereby  the  amine 
compound  first  produced  reacts  upon  the  other  substances  present. 

710.  The  tetrethyl  ammonium  iodide  may  be  converted 
by  moist  silver  oxide  into  tetrethyl  ammonium  hydroxide. 
(C2II5)4XI  +  AgHO  =  (C2H5)4NOII  -f  Agl.     This  hy- 
droxide may  be  obtained  as  a  stable  deliquescent  solid, 
which   resembles   caustic   potash    rather  than    ammonia, 
forming    true    soaps,    and    expelling    ammonia    from    its 
compounds.     Heated  to  100°,  it  breaks  up  into  triethyl- 
amine,  ethylene  and  water, 


AMINES  AND  AMIDES.  379 

It  has  not  been  found  possible  to  obtain  a  body  of  the  formula 
NH5,  nor  of  (C2H5)5N.  The  fifth  bond  of  "ammonium"  nitrogen, 
seems  to  require  a  negative  radical,  like  I  or  NO. 

711.  The  primary  amines   may  be   obtained   pure    by 
the  action  of  nascent  hydrogen  upon  the  nitrils  ;  thus, 
aceto-nitril,  C2II3N  -f  H4  =  C2H5NH2,  ethylamine.     On 
the  other  hand,  they  are  converted  by  nitrous  acid  into 
the    corresponding    alcohol;    as,    C2H5NH2  -f-  HNO2  = 

N~2  -f  H2O  +  C2H5OH  =  ethyl  alcohol.  This  reaction  is 
important,  because  it  is  one  of  the -steps  in  synthesis  by 
which  any  alcohol  can  be  formed  from  the  next  lower 
in  the  series.  It  serves  also  to  distinguish  the  primary 
amines,  inasmuch  as  the  secondary  and  tertiary  amines 
so  treated  form  only  nitroso-compounds;  as, 

(CH3)2NII  -f  IIN02  =  H20  +  JST(CH3)2NO  = 

nitroso-dimethylamine. 

The  simplest  of  all  these  compounds  is  hydroxyl-amine, 
NH2OH,  which  is  easily  formed;  as,  the  hydrochloride, 
NHgO-HCl,  by  reducing  nitric  ether  with  tin  and  hy- 
drochloric acid.  It  is  a  strong  base,  not  as  yet  isolated, 
which  may  be  regarded  as  an  ammonia  in  which  an 
atom  of  H  has  been  replaced  by  hydroxyl. 

712,  The  methylamines  are   found  in  many  plants,  as 
chenopodium  vulvaria,  ergot,  and  usually  among  the  prod- 
ducts  of  decay,  as  in  rotting  grain. 

Methylamine,  CH3NH2,  is  an  easily  inflammable  gas, 
liquid  below  0°C.  Water  at  12.5°C  absorbs  1150  times 
its  volume  of  the  gas,  forming  a  solution  which  has  most 
of  the  properties  of  aqua  ammonia. 

Di-methylamine,  (CH3)2¥H,  is  isomeric  with  ethyl- 
amine, C2H5NH2,  but  has  a  lower  boiling  point. 

Tri-methylamine,  (CH3)3N,  is  found  largely  in  her- 
ring pickle,  to  which  it  gives  its  peculiar  odor,  and  is 
prepared  on  a  large  scale  from  the  dry  distillation  of  the 


380  ORGANIC  CHEMISTRY. 

residue  left  in  making  beet  sugar.  It  is  a  liquid,  boil- 
ing at  9.3°C,  exceedingly  soluble  in  water.  It  is  iso- 
meric  with  propyl  amine,  (13H7NII2. 

713.  The   primary  ethyl   amine,    C2H5NII2,   may    be 
obtained   by  heating  ethyl  isocyanate  with   caustic  pot- 
ash, C2H5CNO  +  2KIIO  ==  K2C08  +  C2H5NH2.     The 
other   ethyl   amines   are   derived   from   this    by   heating 
with  ethyl  bromide. 

714.  Normal   propylamine,   CH8  •  CII2  •  CII2-  NII2,  is 
prepared  from  ethyl   cyanide  by  the  action  of  zinc  and 
hydrochloric    acid,   C2H5CN  +  II2  ^  C8II7NIIa.     It   is 
an  alkaline  liquid  ;  sp.  gr.,  0.73;  boiling  point,  49°C.     It 
has  five  isomers.     The  article  usually  sold  by  this  name 
is  tri-methyl  amine. 

There  are  also  higher  hotnologuew, —  butyl  amine,  amyl  amine, 
etc.  All  these  resemble  those  described,  but  are  of  greater  density 
and  higher  boiling  point. 

715.  Precisely  analogous  to  the  amines  are  the  phos- 
phines  formed  from  PII3  by  the  action  of  the  alcoholic 
iodides;  as,  P(C2II5)8,  tri-othyl   phosphine. 

Tri-ethyl  phosphine  fs  a  valued  test  for  carbon  di-sul- 
phide,  with  which  it  forms  red  crystals,  (C2H5)3PSCS. 

716.  Arsenic    forms    bases    somewhat    similar    to    the 
amines  ;  as, 

(CH3)3As,  tri-methyl  arsene,  and 
(CH3)4AsOH,  tetra-methyl  arsonium  hydrate. 

Cacodyl,  (CH3)2As  •  As(CH3)2,  is  obtained  in  small 
quantity  by  the  dry  distillation  of  arsenious  oxide  and 
potassium  acetate.  *  The  principal  product  is  cacodyl 
oxide, 

4(CH3COOK)+A8203-2K2C03-f2Cb2+(2CH3,As)20. 

This  impure  oxide  evolves  poisonous  vapors  of  a  disa- 
greeable odor,  which  are  spontaneously  inflammable. 


ORGANO-METALLIC  COMPOUNDS.  381 

With  HC1  it  yields  Cacodyl  chloride,  (CH3)2AsCl,  from  which 
pure  cacodyl  may  be  obtained  by  the  action  of  zinc  filings, 

2(CH8)aAsCl  +  Zn  =  ZnCl2  +  (CH3)aAs  •  As(CH3)2. 

An  ethyl  cacodyl  is  also  known;  both  are  colorless  liquids,  some- 
what heavier  than  water,  evolving  vapors  of  disgusting  odor,  and 
spontaneously  inflammable  in  the  air. 


ORGANO-METALLIC  COMPOUNDS. 

717.  Some  of  the  metals,  but  not  all,  form  basic  com- 
pounds with  alkyl  radicals.  This  union  is  brought  about 
(1)  by  heating  in  a  stone  vessel  an  alkyl  iodide  with  a 
positive  metal  or  its  sodium  alloy;  as, 


2C2H51  +ZnNa2  -=2NaI  +  (C2H5)2Zn,  or 

(2),  by  decomposing  a  zinc  compound  so  formed  by  the 
chloride  of  a  less  positive  metal  ;  as, 

2(C2H5)2Zn  +  2PbCl2  =2ZnCl2  +  (C2H4)4Pb. 

These  compounds  are,  for  the  most  part,  volatile  bodies, 
spontaneously  inflammable  when  -exposed  to  the  air,  and 
exceedingly  active  as  chemical  re-agents. 

The  compounds  of  zinc  are  usually  taken  as  a  starting-point. 
Zinc  methyl,  (CH3)2,  Zn.  ;  zinc  ethyl  (C2H5)2,  Zn.,  etc.,  resemble 
each  other,  like  the  members  of  other  series.  The  lower  members 
are  colorless  liquids,  somewhat  heavier  than  water,  and  of  low 
boiling  point  (from  46°  to  200°),  and  yielding  white  vapors  of  a 
peculiar,  unpleasant  odor. 

718.  The  readiness  with  which  these  bodies  are  de- 
composed by  water,  and  by  the  haloid  elements,  espe- 
cially fit  them  for  the  synthesis  of  organic  compounds. 
For  examples:  (1)  Zinc  methyl  (CH3)2Zn,  treated  with 
free  iodine,  yields  ZnI2,  and  methyl  iodide,  CH3I  =  an 
alkyl  haloid  ;  (2)  by  the  reaction  of  this  upon  a  fresh 


382  ORGANIC  CHEMISTRY. 

portion,  a  paraffin  is  formed,  2(CH8I) -f  (CH8)2Zn  = 
ZnI2 -}-2(C2H6),  ethane.  Similarly,  we  may  form  from 
the  acid  chlorides  (3)  ketones;  as, 

2CII3COC1  -|-  (C2H.)2Zn  = 

ZnCla  +  2(CII3-  CO  •  C2II5)  =  methyl-ethyl  ketonc; 

or   (4),  in   the  presence  of  water,  tertiary  alcohols;   as, 

CII3COC1  +  2(CII3)2Zn  +  211,0  - 

CII8ZnCl  -f  CII4  -f  Zn(OII)2  -f  CU8  •  COH  •  (CII8  )2  = 

tertiary  butyl  alcohol. 

These  zinc  organic  compounds  form,  with  sodium  and  potas- 
sium, mixtures  which  contain  similar  compounds  of  the  alkalies. 
These  mixtures,  exi>osed  to  carbonic  anhydride,  yield  a  salt  of  the 
fatty  acid  next  higher  in  the  series;  e.  </., 

C2H5Na  f  CO2  =  C2II5COONa  =  sodium  propionate. 

719.  The  amides  may  be  obtained  (1)  by  heating  am- 
monium salts   to    expel    one   molecule  of  water;    as,  am- 
monium  acetate  =  CII8COOXII4  —  II2O  =  CII8COXII2 
becomes  acetamide;   and  (2),  by  the  action  of  ammonia 
upon  acid  chlorides  ;   as,  acetyl  chloride, 

CII8COC1  -f  XII8  =  HC1  -f-  CII8COXII2. 

Hence,  they  contain  both  acid  and  ammonia  radicals, 
and  act  as  indifferent  bodies,  capable  of  uniting  with 
acids  or  with  metals. 

720.  The  mono-hydric  acids  can  each  form  one  primary 
amide    by    the    substitution   of   XJI2    for   hydroxyl;    as, 
form-amide,  HCOXII2,  from  formic  acid,  IICOOI1,  and 
acetamide,  whose  preparation  has  already  been  indicated. 

The  amides  of  the  monobasic  acids  are  generally  sol- 
ids, crystallizable,  volatile,  frequently  of  characteristic 
odor.  They  are  characterized  by  the  fact  that  on  being 
boiled  with  the  alkalies,  they  reproduce  the  acids  or  the 
ammonia  salts  from  which  they  were  obtained;  as, 

CH3COXH2  -f  H20  =  CH3COOH 


AMINES  AND  AMIDES.  383 

721.  Secondary  monamides  contain  amidogen  united  to 
two  monovalent  radicals;  as,  di-acetamide,  (CH3CO)2NH. 
Alkalamides  are  formed  by  heating  the  amines  with  acid 
ethers  or  chlorides,  as  ; 


CH8COC1  +  C2H6NII2  =  IIC1  +  (C2II5),   (C2II80)NII. 

They  contain  both  acid  and  alkyl  radicals.  The  imides 
contain  one  bivalent  acid  radical;  as, 

lactimide,  (C8II4O)  :NII;  succinimide,  C2H4(CO2)2NH. 

722,  The  tertiary  monamides  contain  triatomic  nitro- 
gen.    They  may  contain  three  monovalent  carbon  radi- 
cals, or  one  monovalent  and  one    divalent;    as,  triaceta- 
mide,   (CII3GO)3N.     They   are   formed    by   heating  the 
secondary  amides  with  acid  chlorides  ;  as, 

(C2H6)(C2II  jO)NII  +  CII8COCl  = 

HCl-h  (C2II6)(C2H80)2N  =  othyl  diacetamide. 

The  nitrils  contain  a  trivalent  carbon  radical,  and  may 
be  formed  from  primary  amides  by  the  action  of  phos- 
phoric anhydride. 

723,  The  nitrils  are  identical  with  the  cyanogen  ethers, 
aceto  -  mtril,  C2H3N,   being   the   same   as   methyl   cyan- 
ide, CH3CN.     They   are   also   prepared   by   heating   po- 
tassium   cyanide  with    a   potassium  alkyl   sulphate,  like 
KCH3SO4;  but  when  so  prepared,  they  are  accompanied 
by    their    metamers,   the    isocyanides.     These    latter    are 
usually  prepared   from  a  mixture  of  chloroform  and  an 
alcoholic  solution  of  potassium  hydroxide  with  an  amine, 
and  hence  are  called  the  carb-amines. 

The  two  series  differ  at  all  points.  The  carbamines  are  poison- 
ous, of  nauseous  odor,  of  great  chemical  activity,  decomposed  by 
boiling  with  water  plus  an  acid  into  formic  acid,  and  an  amine 
salt;  as,  CH3  NC+H2O+HC1=HCOOH+CH3NH2  •  HC1,  methyl- 
ainine  hydrochloride,  and  by  AgHO  into  a  cyanate;  as,  CH3CNO. 

The  nitrils  are  not  oxidized  by  AgHO.  They  are  decomposed 
by  boiling  with  water  plus  an  acid  into  an  ammonium  salt,  and 


384  ORGANIC  CHEMISTRY. 

the  fatty  acid,  which  is  next  higher  in  the  carbon  series;  as,  from 
methyl  cyanide,  CH8CN  +  H2o"-r  HC1  =  NII4C1  +  CH.COOII  = 
acetic  aci<l.  Their  odors  are  not  unpleasant,  and  they  are  not  re- 
garded as  poisonous;  they  are  also  of  higher  boiling  |>oint  than  the 
corresponding  isocyanides. 

724.  Acids   containing   one   or  more   hydroxyl   groups 
may  give   rise  to  a  great  variety  of  amide  compounds, 
which    are    structurally    derived    from    their    ammonium 
compounds  by  the  removal  in  succession  of  one  or  more 
molecules  of  water.     For  example,    the  acid   ammonium 
Hiiccinate,  COXII4,  r2II4,  COO II,  yields  an  acid  amide; 
succinamic  acid,  COXTI2,  C2II4,  COOII,  and   then   suc- 
cinimide,  C2H4(CO)2NII.     The  normal   ammonium  suc- 
cinate,  C2H4(COONH4)2,  yields  first  succinamide, 

C2H4(CONH2)a, 

and  then   succino-nitril.  C2II4(CX)2. 

725.  The    amic    acids    are    intermediate    between    the 
acids  of  the  fatty  and  lactic  scries,  and  are  termed  ala- 
nines.     For   example,    amid-acetic   acid,    formed    by   the 
action  of  dry  ammonia  upon  eh  lor  acetic  acid, 

CH2Cl  •  COOII  +  2NH3  =  NII4Cl  -f  CH2XII2  •  COOH, 

is  glycocine,  and  may  be  converted  to  glycollic  acid  by 
oxidation  with  nitrous  acid. 

CH3               CH2NH2               CH2OH  CH2OH. 

I  I  I 

COOH            COOH                   COOH  CONH2. 

Acetic  acid.  Glycocine.  Glycollic  acid.  Glycollamide. 

The  same  relations  exist  between  propionic  acid,  alanine,  and  lactic- 
acid;  caproic  acid,  leucine  and  leucic  acid. 

726.  Amid-acetic   acid,   or  glycocine,   is  obtained   by 
boiling  hippuric  acid  with  hydrochloric  acid  and  water: 

C7H5O  •  NH  •  CH2  COOH  +  H2O  = 

C6H5COOH  (benzoic  acid)  +  CH2XH2-COOH. 


AMINES  AND  AMIDES.  385 

It  forms  rhombic  prisms,  which  have  a  sweetish  taste, 
and  combines  both  with  acids  and  bases.  It  forms  many 
products  by  substitution,  among  which  are  to  be  noted 
(1)  its  amide,  CH2NH2- CONH2,  amido-acetamide,  which 
is  formed  by  heating  glycocine  with  alcoholic  ammonia 
to  155°C;  (2)  its  alkyl  derivatives;  as,  sarcosine  = 

CH2-NHCH3-COOII, 

which  is  obtained  by  heating  creatine  with  barium  hy- 
droxide. Creatine  is  formed  artificially  by  heating  sar- 
cosine  with  cyanamide,  and  is,  therefore,  methyl-glyco- 
cine-cyanamide, 


It  is  always  present  in  meat  juice,  and  may  be  prepared 
from  the  flesh  extracts.  Creatinine,  C4H7N3O,  is  a  de- 
composition product  of  creatine,  and,  as  such,  is  found 
not  in  flesh,  but  in  urine  (0, 


These  bodies  probably  contain  the  same  complex  radical,  guan- 
idine  (NH:C:  (NH)2)",  as  in  guanine,  C5H5N5O,  which  is  found 
along  with  uric  acid  in  guano.  Allied  to  these,  but  containing  the 
radical  of  urea  (NH2  •  CO  •  NH2),  are  the  three  following,  which 
also  occur  in  flesh  juice;  viz, 

Gamine,  C7H8N4O3,  oxidized  by  nitric  acid  to  sarcine,  or  hy- 
poxanthine,  C5H4N4O,  and  xanthine,  C5H4N4O2. 

727.  Homologous  with  xanthine  are  two  widely  dis- 
tributed vegetable  bases;  viz,  Theobromine,  C7H8N4O2, 
which  is  the  active  principle  of  the  cacao  beans,  and 
its  methyl  derivative,  caffeine,  C8H10N4O2,  the  alkaloid 
of  coffee  and  tea.  Both  may  be  obtained  by  treating 
their  aqueous  infusions  (1)  with  lead  acetate  to  remove 
extraneous  matters;  (2)  filtering  and  freeing  the  filtrate 
from  lead  by  H2S;  (3)  evaporating  to  dryness  and 
extracting  the  alkaloid  from  the  residue  by  absolute 
alcohol. 

Chem.—  25. 


386  ORGANIC 

They  are  white,  crystalline  bodies,  of  bitter  taste, 
slightly  soluble  in  water,  and  producing,  when  swal- 
lowed in  overdoses,  great  nervous  excitement. 

Their  use  in  the  common  beverages  is  well  known,  but  it  is  not 
BO  generally  recognized  that  "  beef  tea"  contains  bodies  so  closely 
related,  not  only  in  chemical  structure,  but  in  physiological  action. 

728.  Betaine,  C^II^NO,,,  which  is  found  in  beet  juice 
(\%\  is  tri-methyl  glycocine.     When  melted  with  caustic 
potash  it  evolves  tri-methylamine. 

Choline  is  important  because  so  widely  disseminated, 
being  found  in  many  plants  as  sincaline;  in  the  bile 
(whence  its  name);  in  the  lecithins  (p.  407),  and  in  the 
brain,  as  neurine.  It  is  a  complex  amine  base, 

(C2H4OH)-N(CH8),OII  = 

ethylene  hydrate  tri-methyl  ammonium  hydroxide,  and 
may  be  prepared  from  white  of  eggs,  or  from  brains,  as 
a  strongly  alkaline  syrup. 

729.  Ox-bile   contains   also    the    sodium   salts   of  two 
amide-acids.      One    of   these,    glycocholic,    C26H43NO6, 
yields,  on  being  boiled  with  water,  cholic  acid,  C24II40O5, 
and  glycocine;  the  other,  taurocholic  acid,  C26H45NSO7, 
yields  cholic   acid   and   taurinc.     Taurine  is  amid-ethyl- 
sulphonic-acid==C2H4NII2-  SO2OH.     Cholic  acid,  when 
mixed  with  a  little  sugar,  and  then  with  strong  H2SO4, 
yields  a  beautiful  purple  color.     (Pettenkofer's  test.) 

730.  Leucine  is  amid-isocaproic  acid, 

(CH3)2 :  CH  •  CH2-  CH,  NH2-  COOH, 

and  is  found  in  many  animal  organs,  pancreas,  brain, 
etc.  It  is  obtained  from  gelatin  (along  with  glycocine), 
and  from  the  albuminoids  (along  with  tyrosine),  as  a 
product  of  putrefaction.  The  tyrosine  is  probably  an 
aromatic  glycocine,  HO  •  C6H4-  C2H3-  NH2-  COOH,  and 
is  less  soluble  than  leucine. 


UREA.  387 

Leucine  crystallizes  in  pearly  plates  (sp.  gr.,  1.3)  from  its  boiling 
solution  in  alcohol,  and  yields,  with  suitable  oxidizing  agents,  leucic, 
valeric,  and  caproic  acids. 

731.  The  amides  of  carbonic  acid  may  be  considered  as 
derived  from  acid  ammonium  carbonate,  NII4O  -CO  •  OH, 
and  normal  ammonium  carbonate,  NH4O  •  CO  •  ONH4. 
Both  of  these  are  found  in  the  commercial  sal-volatile, 
as  is  also  a  third  body,  ammonium  carbamate, 


This  last  is  also  formed  by  the  direct  union  of  dry  am- 
monia, and  carbonic  anhydride,  2NH3  -f  CO2. 

(1)  The  carbamic  acid,  NH2-  CO  •  OH,  which  it  is  sup- 
posed to  contain,  is  not  known  in  the  free  state,  but  it 
is  represented  by  several  salts. 

When  ammonium  carbamate  is  heated,  it  breaks  up  into  am- 
monium carbonate  and  urea,  or  carbamide, 


2(NH2  •  CO  •  ONH4)  =  CO(ONH4)2-f  CO(NH2)2. 

Carbiniide,  CO  :  NH,  is  probably  identical  with  isocyanic  acid, 
CNOH.  Ammonium  isocyanate,  CNONH4,  when  warmed  with 
water,  is  rapidly  converted  into  its  isomer,  urea,  or  carbamide. 

(2)  Urea,  NH2-CO-KEI2,  is  a  product  of  the  final 
metamorphoses  of  nitrogenous  tissues,  and  is,  therefore, 
found  in  the  blood,  whence  it  is  secreted  by  the  kidneys, 
and  constitutes  from  2  to  3^  of  human  urine.  A  healthy 
man  secretes  about  30  grammes  of  urea  daily. 

732,  Urea  may  be  prepared  from  human  urine  (1)  by 
evaporating  it  to  a  syrup,  cooling,  then  mixing  it  slowly 
with  an  excess  of  strong  nitric  acid.  (2)  Urea  nitrate, 
NH2-CO*NH2,  HNO3,  separates  out  in  white  masses. 
(3)  This  product,  after  being  washed  with  ice  cold  water, 
is  purified  by  recrystallization  from  hot  water.  (4)  The 
urea  nitrate  is  now  decomposed  by  barium  carbonate, 

CO-^H2,  HN08)-J-  BaCO3  = 

Ba(N03)2  +  C02  +  H20  +  2(NH2-  CO  • 


388  ORGANIC  CJTEmSTRY. 

the  mixture  evaporated  to  dryness  ;  and,  finally  (5),  the 
urea  is  extracted  by  means  of  strong  alcohol. 

Urea  is  the  first  organic  compound  artificially  pre- 
pared, and  may  be  obtained  in  a  state  of  great  purity  by 
boiling  an  aqueous  solution  of  ammonium  isocyanate  for 
a  short  time  (p.  312),  then  evaporating  to  dryness,  and 
recry stall izing  from  its  solution  in  alcohol. 

Urea  is  soluble  in  water  and  hot  alcohol.  Its  crystals 
resemble  those  of  saltpetre  in  shape,  odor  and  taste.  It 
combines  by  direct  addition  with  acids  and  with  salts; 
as,  urea  hydrochloride,  CO(NH2)2HC1,  urea  sodium 
chloride,  CO(NII2)2NaCl,  H2O. 

When  urea  is  heated,  it  melts  at  132°C,  and  is  decomposed  at 
150°  into  ammonia  and  a  residue  containing — 

biuret-    NH./'O     Nil     CONII2, 

and  oyanuric  acid,  C'^X^IIjO^.  On  further  heating,  the  eyanuric 
acid  becomes  cvanic  acid.  Urea  is  also  decomposed  by  long  boiling 
with  water,  yielding  ammonium  carbonate,  and  more  readily  in  the 
presence  of  ferments,  such  as  are  found  in  putrefying  urine.  Dilute 
solutions  of  urea  when  treated  with  the  hypobromites  in  excess  of 
alkali  give  the  reaction: 

CO(NII2)2  +  3NaBrO  -f  2NaHO  =  SNaBr  +  H2O  +  Na2CO3  +  8"2. 

Inasmuch  as  all  the  nitrogen  escapes  in  the  gaseous  form,  this  re- 
action may  be  used  as  a  quantitative  test.  One  gramme  of  urea 
should  evolve  373CC  of  free  nitrogen. 

733.  Compound  ureas  are  formed  from  carbamide  by 
replacing  a  portion  of  its  hydrogen  with  alkyl  or  acid 
radicals. 

(1)  The  alkyl  derivatives  are  prepared  from  potassium  cyanate 
by  the  action  of  the  amine  salts.  They  resemble  urea  in  their 
general  properties  ;  but  when  boiled  with  potassium  hydrate  yield 
the  amines  instead  of  ammonia. 

Ethyl  urea  is  NH2  •  CO     NH     C2H5; 

Di-ethyl  urea  is  C2H3     NH  •  CO     NH     C2H5, 


URIC  ACID.  389 

and  its  metamer,  NH2  •  CO  •  N(C2H5)2.  The  two  first  yield  ethyl- 
amine;  the  test,  di-ethylamine. 

(2)  Compound  ureas  containing  a  rnonatomic  acid  radical  are 
prepared  by  the  action  of  acid  chlorides  upon  carbamide;  thus, 

Acetyl-urea,  NH2  •  CO  •  NHC2H3O,  is  produced  when  acetyl 
chloride  is  poured  upon  urea,  and  forms  long  silky  needles,  which 
are  decomposed  at  high  temperatures  into  acetamide  and  cyanuric 
acid. 

Compound  ureas  are  also  formed  by  the  action  of  various  agents 
upon  uric  acid.  These  contain  divalent  acid  radicals,  like — 

Oxalyl,         •  CO  •  CO    ; 
Mesoxalyl,   •  CO  •  CO  •  CO  •  ;  and 
Tartronyl,       CO  •  CHOH  •  CO. 

734.  Uric  acid,  C5H4N4O3,  is  a  diureide,  for  which 
the  following  structural  formulae  have  been  proposed: 

NH  — CO  NH  —  C-       NH 

I 
CO       C  — NH  &        CO 


xco 


CO  — CO 


— C  — NHX  NH  — C  NH 

It  occurs  as  urates  of  soda  and  ammonia  in  the  urine 
of  all  flesh-eating  animals,  very  abundantly  in  the  ex- 
crements of  serpents.  Normal  human  urine  contains 
about  0.1^,  but  in  some  diseases  (gout,  etc.)  it  is  more 
abundant,  and  may  form  red  deposits  on  standing. 

It  is  prepared  from  guano  (1)  by  heating  with  sodium 
hydrate  solution  so  long  as  the  fumes  of  NH3  are  given 
off;  and  (2),  pouring  the  filtered  liquid  into  dilute  hy- 
drochloric acid.  Uric  acid  separates  out  as  a  heavy 
white  crystalline  powder  almost  insoluble  in  cold  water 
and  alcohol,  but  somewhat  soluble  in  strong  alkalies.  Its 
lithium  salts  are  characterized  by  their  great  solubility. 

Uric  acid  yields  a  great  variety  of  products  when  acted  upon 
by  oxidizing  agents,  forming,  in  alkaline  solutions,  diureids;  as, 
uroxanic  acid,  C5H8N4O6;  cdlantoin,  C4H6N4O3.  It  yields  attoxan, 
C4H2N2O4,  when  digested  with  strong  nitric  acid. 


390  ORGANIC  CHEMISTRY. 

735.  Alloxan  passes  by  the  action  of  reducing  agents 
to   aUoxantin,   C8H4N4O7,   311 2O,   and   to  dialuric  acid, 
C4H4N2O4.     These  are  converted  by  the  action  of  am- 
monia into  dialuramide  or  uramil,  C4II5N3O3.     Various 
mixtures  of  these   four  substances  are   employed   in   the 
manufacture  of  murexide,  which   is  a  valuable  red  dye- 
stuft'.     Murexide  is  the  ammonium  salt  of  purpuric  acid, 
C8H4N5OG,  NH4,  and  crystallizes  from  its  hot  solution 
in    gold-green    plates.     The  murexide    test   for  uric   acid 
is  very  delicate.     It  is  made  by  dissolving  a  small  quan- 
tity of  uric  acid  in  nitric  acid,  evaporating  carefully  to 
dryness.     The  residue,  treated  with  potash,  becomes  vio- 
let ;  treated  with  ammonia,  purple.     Murexide  was  once 
used  as  a  purple  dye. 

736.  Hippuric  acid,  C9TI9NOV  takes  the  place  of  uric 
acid  in  the  urine  of  stall-fed  horses  and  cows  (1^);  and 
is  also  found  in  minute  quantity  in  human   urine.     It  is 
decomposed  by  boiling  into  glycocine  and  benzoic  acid. 

C9H9N03  +  II20  =  CH2NII2-  COOJI  +  C6II5COOU. 


Recapitulation 


(1)  Any   hydrogen    atom   in   NH3   or  in   NII4C1    may  be   replaced 
by  other  radicals. 

(2)  When  alkyl  radicals  are  substituted  for  hydrogen,  an  amine  is 
formed. 

(3)  When  an  acid  radical  is  substituted  for  hydrogen,  an  amide  i» 
formed. 

(4)  When   an   alkyl,  and  also  an  acid,  radical   are  substituted,  an 
alkalnmide  is  formed. 

(5)  So   also   the  metals  may  form  organo-metallic  compounds   by 
the  displacement  and  substitution  of  the  hydrogen  in  ammonia 
or  ammonium. 


RECAPITULATION.  391 

(6)  The  amic  acids,  or  alanines,  contain  the  (NH2)X  group  in  the 
alkyl  radical  and  carboxyl,  COOH. 

(7)  The  alkalamides  have  both  acid  and  alkyl  radicals,  as  ethyl- 
acetamide. 

(8)  The  amines  are  strong  bases,  and  combine  with  acids  by  addi- 
tion.    The  primary  amides  act  both   as   bases  and   acids;   the 
others  generally  act  as  weak  acids. 


II. 

These  compounds  are  mono  if  but  one  ammonia  molecule  is  so 
changed;  di  if  two,  etc.,  etc.  They  are  primary  if  but  one  H  in 
the  NH3  molecule  is  exchanged;  secondary  if  two  H's  are  exchanged; 
tertiary  if  three, 

III. 

These  bodies  are  of  immense  importance  in  both  the  vegetable 
and  animal  kingdoms. 

The  amines  are  frequently  found  in  growing  plants,  as  betaine, 
and  are  related  to  some  of  the  alkaloids,  as  creatine  and  caffeine. 
The  amides  are  frequently  produced  by  the  decomposition  of  al- 
bumin and  gelatin. 

The  amides  of  carbonic  anhydride  form  a  great  number  of  the 
products  of  the  decomposition  of  animal  tissues,  like  urea,  uric 
acid,  purpuric  acid. 


CHAPTER   XXV. 

THE    ETHERS. 

737.  The  term  ether  is  usually  employed  to  include  a 
vast  number  of  substances  which  agree  in  containing  at 
least  one  alkyl  radical;  as,  CII8I,  methyl  iodide;  CH8CN, 
methyl  cyanide;  CH3  O   CH3,  methyl  oxide;  CH3  S  CH8, 
methyl  sulphide;   CII8-  O  •  C2II5,  methyl-ethyl  oxide;  and 
CII8-  O-CII3O,  methyl  formate.     It  lias  been  found  pos- 
sible  to  classify   these   in  groups,  like   the    four  already 
defined  upon  page  298. 

I.  Haloid  ethers,  including  the  cyanides. 

II.  Simple  ethers,  the  oxides,  sulphides,  etc. 

III.  Mixed  ethers,  with  two  different  alkyl  radicals. 

IV.  Ethereal  salts,  containing  also  an  acid  radical. 

738.  The  haloid  ethers,  containing  chlorine  and   bro- 
mine,  may   be    prepared    by   the    direct   action    of  these 
elements  in  the  sunlight  upon  the  paraffins;  as, 


Usually,  all  are  obtained  from  the  anhydrous  alcohols 
by  the  action  of  the  haloid  compounds  of  phosphorus; 
as,  CHgOH  +  PBr5  ==  HBr  +  POBr8  +  CII8Br.  More 
frequently  in  the  case  of  bromine  and  iodine  by  a  mix- 
ture of  these  elements  with  phosphorus;  as, 

4CH8OH  +  I.  +  P  =  PO(OH)3  -f  HI  +  4CH3I. 

Each   alkyl   radical  may  have  a   full  series  of  chlor- 
ides, bromides,  iodides,  and  cyanides.     By  far  the  greater 

(392) 


THE  ETHERS.  393 

number  are  of  interest  only  as  items  necessary  to  render 
such  series  complete.  They  are  generally  colorless  liq- 
uids, freely  soluble  in  alcohol,  and  but  slightly  in  water. 
The  lower  members  volatilize  readily,  yielding  vapors  of 
characteristic  odors,  which  are  often  fragrant  and  usually 
exceedingly  inflammable. 

They  are  very  susceptible  to  chemical  change,  and  ^are  of  great 
use  in  synthetical  operations  (especially  the  iodides),  as  is  exhibited 
by  the  following  general  reactions  of  the  haloid  ethers : 

I.  With  nascent  hydrogen  =  the  paraffins;   as, 

CH3C1  +  IIC1  +  Zn  =  ZnCl2  +  CH4. 

II.  With  metallic  zinc  =  the  organo-base;  as, 

2CH3C1  +  2Zn  =  ZnCl2  +  (CH3)2Zn. 

III,  With  ammonia  —  the  amines;  as, 

CH3I  +  NH3  =  HI  +  CH3NH2. 

IV.  With  NallO  or  AgHO  =  the  alcohols;  as, 

CH3I  +  AgHO  =  Agl  +  CH8OH. 
V.  With  sodium  alcoholate  =  the  ethers;  as, 

CH3I  +  CH3ONa  ==  Nal  +  CH3  •  O  •  CH3. 
VI.  With  silver  salts  of  the  organic  acids  =  the  ethereal  salts; 

as,  CH3I  +  H:  COOAg  =  Agl  +  CH3  •  O  •  CHO. 
VII.  With  potassium  cyanide  =  the  cyanides;  as, 

CH3I  +  KCN  =  KI  +  CH3CN. 
VIII.  With  KCNS  =  the  sulpho-cyanates;  as, 
CH3I  +  KCNS  =  KI  +  CH.CNS. 
IX.  With  KHS  =  the  mercaptans;  as, 
CH3I  +  KHS  =  KI  +  CH3SH. 

739.  Methyl  chloride,  CH3C1,  is  easily  prepared  by 
heating  together  methyl  alcohol,  common  salt,  and  strong 
sulphuric  acid.  It  is  a  gas  which  may  be  liquefied  at 

22°C.     By  the  action  of  chlorine  in  sunlight,  it  yields 

in  succession,  CH2C12,  methene  chloride;  CHC13,  methenyl 
chloride ;  and  CC14,  carbon  tetrachloride. 


394  ORGANIC  CHEMISTRY. 

740.  Chloroform,  CHC13,  is  usually  prepared  from  al- 
cohol.     This    is    mixed  with    32    parts    of  water  and    10 
parts  of  chloride  of  lime;  heated  quickly  until  the  reac- 
tion   begins  and   then   distilled.     The   chloroform    passes 
over  with  the  first  portions,  mixed  with  water,  but  soon 
settles  out   by  reason   of  its  insolubility  in   water.     The 
crude  choloform  is  purified  by  washing  with  water  and 
by  redistillation. 

Chloroform  is  a  colorless  liquid  of  sweetish  taste  and 
pleasant  odor;  density,  1.525;  boils  at  G3.5°0.  It  burns 
with  a  greenish  flame,  but  is  not  easily  ignited.  It  is 
remarkable  for  its  anaesthetic  powers,  its  vapors,  when 
inhaled,  speedily  producing  insensibility  to  pain.  It  is 
also  an  excellent  solvent  for  many  resins  and  alkaloids, 
and  for  Br,  I,  P,  etc. 

When  boiled  with  an  alcoholic:  solution  of  caustic  potash,  it  is 
converted  to  potassium  formate, 

CHCl.,  +4KIIO  — 2II2()  + 3KC1-I-H,  COOK; 

but  if  ammonia  is  at  the  same  time  present,  potassium  cyanide  is 
formed,  <'HU3  +  NII3  -f  4KIIO  =  4H2O  -f  3KC1  +  KCN.  When 
boiled  with  chlorine  in  the  sunlight  it  yields  carbon  tetrachloride, 
CC14,  a  colorless  liquid  of  ethereal  odor;  density,  l.oG;  boils  at 
78°C.  Nascent  hydrogen  changes  CC14  by  retrograde  steps  into 
CIIC13,  CILC1,,  ('Had,  and  to  CII,. 

741.  Bromoform,  CITBr3,  and  iodoform,  CHI8,  are  ob- 
tained by  heating  an  alcoholic  solution  of  caustic  potash 
with    bromine    or    iodine,    avoiding   excess.      Bromoform 
is  a  liquid  which    resembles  chloroform,  but  has  almost 
double    the    density    (2.9),    and    a    higher    boiling    point 
(152°C). 

lodoform  crystallizes  in  yellow  leaflets,  which  smell 
like  saffron.  It  is  used  in  medicine  in  place  of  free 
iodine  (see  page  324). 

742.  Ethyl  chloride,  CH6C1,  is  prepared  by  saturating 


THE  ETHERS. 


395 


cold  absolute  alcohol  with  dry  hydrochloric  acid  gas. 
After  standing  some  days  in  stoppered  vessels,  the  prod- 
uct is  distilled  upon  a  water-bath,  and  the  vapors  con- 
densed in  a  receiver,  surrounded  by  ice  and  salt.  It  is 
an  extremely  volatile  liquid;  sp.  gr.,  0.92;  boiling  point, 
12°C.  With  chlorine,  in  sunlight,  it  yields  all  the  other 
chlorides  of  the  ethyl  radical, 

C2II4C12,  C2H3C13,  C2H2C14,  C,IIC15,  and  C2C16. 

The  first  of  these  is  CII3-  CHC12,  ethylidene  chloride,  a 
fragrant  liquid  boiling  at  GO0,  which  may  be  supposed 
to  contain  the  radical  (CII3-CH)",  or  ethylidene.  It  is 
isomeric  with  the  following: 

Ethylene  chloride,  C1II2C  •  CII2C1,  was  long  known 
under  the  name,  Dutch  liquid.  When  pure,  it  is  a  thin 
liquid,  of  sweetish  taste,  and  an  odor  resembling  chloro- 
form; boils  at  85°C;  density,  1.27.  It  is  prepared  by 
mixing  equal  volumes  of 
dried  chlorine  and  olefi- 
ant  gas  in  a  capacious 
globe  (see  Fig.  106).  The 
combination  takes  place 
rapidly,  and  the  product 
trickles  down  into  a  cooled 
receiver,  which  should  be 

provided  with   an   escape 

FIG.  106. 
pipe  tor  any  uncondensed 

gases.  This  crude  product  is  washed  with  water,  dried 
by  strong  sulphuric  acid,  and  redistilled. 

A  large  number  of  chlorides  may  be  obtained  from  this  by  suc- 
cessive treatment:  (1)  with  potassium  hydroxide,  which  removes 
one  chlorine  atom;  as,  C2H4C12+KOH=KC1+H2O-J-C2H3C1;  and 
then  (2),  with  chlorine,  which  again  adds  two  (C2H3C13).  These 
products,  together  with  those  formed  from  ethane  or  ethyl  chloride, 
are  given  in  the  following  table,  together  with  their  boiling  points. 
It  will  be  noticed  that  there  are  three  pairs  of  isorners.  The  table 


396 


ORGANIC  CHEMISTRY. 


is  an  illustration  of  the  variety  of  compounds  which  may  be  pro- 
duced by  chlorine,  bromine,  and  iodine  upon  the  hydrocarbons  and 
their  alcoholic  derivatives.  Compounds  are  also  known  which  con- 
tain two  haloids;  a.s,  chlor-iod-ethylene,  CIF2C1  •  CII2I. 


KKO.M  ETIIYLENE. 

FROM  ETIIANK. 

HY  SI-BSTITUTION. 

11  Y  ADDITION. 

Ethylene, 

Ethylene 

Ethyl  chloride, 

di-chl 

oride. 

CH2f        boiling  pt. 

CII2C1,  lx>iling  pt. 

CII3,        boiling  pt. 

||                   -110°. 

1 

85°. 

|                      12°. 

CHa. 

CH2C1. 

CII2C1. 

Chlor  ethylene, 

Chlor  ethylene 

Di-chlor  ethane, 

di-chloride, 

CII2,        boiling  pt. 

CII2CI,   boiling  pt. 

CII3,        boiling  pt. 

-18°. 

i 

115°. 

59°. 

CIIC1. 

CHC12. 

CHC12. 

Di-chlor  ethylene, 

Di-clilor 

ethylene 

Tri-chlor  ethane, 

di-chloride, 

CHC1,      boiling  pt. 

CHC12,  boiling  pt. 

CII3,       boiling  pt. 

II                    37°. 

I 

137°. 

|                     75°. 

CHC1. 

CHG12. 

CC13. 

Tetra-chlor  ethane, 

CII2C1,    boiling  pt. 

102° 

CC13. 

Tri-chlor  ethylene, 

Penta-chlor  ethane, 

CHC1,              boiling  pt. 

CHC12,          boiling  pt. 

||                             88°. 

|                            158°. 

CC12. 

CC13. 

Tetra-chlor  ethylene, 

Per-chlor  ethane, 

CC12,                boiling  pt. 

CC13,              boiling  pt. 

|                            117°. 

182°. 

CC12. 

CC\3. 

THE  ETHERS.  397 

743.  The  halogen  compounds  of  the  higher  carbon  nu- 
clei  increase   theoretically  very  rapidly.     Only  a  small 
part  of  these  are  known,  and  few  of  these  of  practical 
importance. 

For  example,  the  three  carbon  nucleus  includes  such  bodies  as 
propane,  C3H8;  propent,  C3H6;  allylene,  C3H4,  and  their  alcohols 
propyl,  isopropyl,  C3H7OII;  propyl  glycol,  C3H6(OH)2,  and  glycerol, 
C3H5(OII)3,  each  with  its  own  series  of  derivatives. 

Of  these,  allyl  iodide,  C3H5I  or  CH2:CH  •  CH2I,  may  be  pre- 
pared by  heating  glycerol  with  phosphorus  and  iodine.  It  is  an 
oily  liquid  smelling  strongly  like  leeks.  From  it  may  be  obtained 
allyl  alcohol,  C3H5OH,  and  other  interesting  derivatives,  as  the  ar- 
tificial mustard  oils  and  some  of  the  "hydrins." 

744.  The  term  hydrin  ought  to  be  restricted  to  those 
halogen   ethers   of   the    polyhydric   alcohols   which    still 
contain    hydroxyl,  but  it   is   somewhat   loosely   applied, 
especially  in  case  of  the  halogen  ethers  of  glycerol. 

If  the  glyeols  or  the  glycerols  be  saturated  with  dry  hydro- 
chloric acid  gas,  the  mixture  digested  for  some  time  at  a  moderate 
heat  and  then  distilled,  a  portion  of  the  hydroxyl  of  these  alco- 
hols will  be  replaced  by  chlorine;  as,  glycol  mono-chlor-hydrin, 
CH2C1  •  CH2OH,  and  with  glycerin,  chlorhydrin,  C3H5C1(OH)2, 
and  di-chlorhydrin,  C3H5C12OH.  Isomers  of  the  two  latter  may 
be  formed  from  allyl  iodide.  All  these  are  thin,  colorless  liquids 
of  somewhat  lower  boiling  point  than  the  alcohols  from  which  they 
are  formed.  By  the  aid  of  phosphorus  penta-chloride,  the  last  hy- 
droxyl may  be  displaced,  forming,  for  example,  glycol  di-chloride, 
CH2C1  •  CH2C1,  and  tri-chlorhydrin,  C3H5C13,  which  boils  at  158°C; 
sp.  gr.  1.42. 

Epichlorhydrin,  C3H5OC1,  which  still  more  closely  resembles 
chloroform  (boils  118°;  sp.  gr.,  1.19)  is  prepared  by  mixing  the 
di-chlorhydrins  with  strong  caustic  alkali,  and  shaking: 

C3H5C12OH  +  KOH  =  KC1  +  H2O  +  C3H5OC1. 

745.  The  nitro  paraffins  are  formed  when  silver  nitrite 
is  added  to  the  alkyl  iodides;  as,  C2H.-I  -f  AgNO2  = 
AgI-j-C2H5NO2  =  nitro  ethane.     The  action  is  violent, 


398  ORGANIC  CHEMISTRY. 

and  much  heat  is  given  out.  Sometimes  the  isomeric 
nitrous  ethers,  as  C2H5-  O  •  NO  -.-  ethyl  nitrite,  are  pro- 
duce* 1  at  the  same  time,  but  these  are  of  far  lower  boil- 
ing point,  and  are  easily  separated  by  fractional  distilla- 
tion. The  nitro  paraffins  are  oily  liquids,  quite  stable, 
but  capable  of  forming  compounds  that  are  fearfully  ex- 
plosive; as,  C2H4NaNO2. 

Any  nitro-derimth'e,  when  treated  with  nascent  hydrogen,  is  con- 
verted to  its  amiite;  as,  C2II5NO2  +  H6  =- 2H2O  +  C2H5NH2  = 

ethyl  amine,  which  seems  to  indicate  that  the  nitrogen  in  it  is  di- 
rectly united  to  the  carbon  nucleus.  Those  of  the  "closed  chain" 
series  are  of  great  use  in  synthetical  chemistry;  but  those  of  the 
"oi>en  chain"  are  of  little  importance. 

746.  The   normal   cyanogen   ethers  are   identical    with 
the    nitrils    C^72.'J),  and   are  characterized   by  the   readi- 
ness   with    which    they   exchange    the    cyanogen    for   tho 
carboxvl   irroiip:    as,   in   the  reaction   with    potassium   hy- 
droxide, (MI3-<'N  -f  KILO  -i   I1,0,_NII3    j-ClI8-C<>OK. 

It  will  be  noticed  that  the  acid  thus  formed  has  one  carbon 
atom  more  than  the  alcohol  from  which  it  came.  By  taking  ad- 
vantage of  this  fact,  and  of  the  fact  that  any  acid  may  be  reduced 
to  its  corresponding  alcohol,  all  of  the  alcohols  in  a  given  series 
may  be  obtained  from  the  lirst ;  viz,  by  forming  in  succession  (1) 
the  cyanogen  ether,  (2»  the  acid  salt,  (.'!)  the  acid  of  higher  car- 
bon content,  (4)  the  alcohol  corresponding. 

Only  the  first  five  of  the  alkyl  isocyanides  arc  known. 
In  these  the  nitrogen  is  penta  valent,  as  in  methyl  iso- 
cyanide,  CII3  •  N  j  C,  the  alkyl  radical  being  directly 
united  to  the  nitrogen.  With  potassium  hydroxide,  they 
yield  small  quantities  of  potassium  formate,  and  the  am- 
ine  of  the  alkyl  radical,  instead  of  the  NII3  ;  for  example, 
CII3-N;  C+KHO+H2O-^H-COOK+CH8-NH2.  Acids 
easily  convert  them  to  formic  acid  and  an  amine  salt. 

747.  The  simple  ethers  may  be  prepared  by  heating  a 
sodium  alcoholate  with  an  alkyl  iodide;  as, 

CH3ONa  4-  CH3I  =  Nal  +  CH3-  O  •  CH3  =  methyl  ether. 


THE  ETHERS. 


399 


Mixed  ethers  are  formed  when  two  different  alkyl  radi- 
cals enter  into  the  reaction;  as,  CH3OXa  -f-  C2H5I  = 
Nal  -f  CH3-  O  •  C2H5  =  methyl-ethyl  ether. 

The  usual  process  for  making  the  simple  ethers  con- 
sists in  heating  the  respective  alcohols  with  strong  sul- 


FlG.  107. 


phuric  acid.  The  reactions  which  take  place  in  the 
use  of  ethyl  alcohol  have  been  given  on  page  322.  The 
temperature  required  to  produce  ethyl  ether  by  the  de- 
composition of  the  monoethylic  sulphate  is  about  140°C. 
The  regenerated  sulphuric  acid  is  of  course  in  condition 
to  act  upon  fresh  molecules  of  the  alcohol.  The  process 
is  made  continuous  by  starting  with  a  mixture  that  boils 
at  the  required  temperature,  say  five  parts  of  strong  al- 
cohol with  nine  parts  of  strong  sulphuric  acid. 


400  ORGANIC  CHEMISTRY. 

Fig.  107  exhibits  a  convenient  apparatus.  A  flask  is  provided 
with  a  stopper  having  three  holes;  one  for  a  thermometer,  one  for 
the  supply  of  alcohol,  and  the  last  for  the  escape  of  the  vapors 
into  the  condenser.  As  soon  as  the  liquid  begins  to  distil  at  140°C, 
the  alcohol  is  allowed  to  enter  at  the  bottom  of  the  flask  at  such 
a  rate  that  a  nearly  uniform  temperature  is  maintained.  In  prac- 
tice, there  is  always  a  little  waste,  other  organic  products  are 
formed,  and  sulphurous  acid  evolved;  the  distillate  also  contains 
unaltered  alcohol  and  water.  The  ether  is  purified:  (1)  by  agita- 
tion with  milk  of  lime;  (2)  drying  with  calcium  chloride;  and  (3), 
redistillation. 

748.  Ethyl  ether,   (C2II5)2O,  is  sold   under   the   name 
of  sulphuric   other.      It    is   a   colorless   fluid   of  pleasant 
odor,  so  named   ethereal;   boiling  at  35°(1;   sp.  gr.  0.74. 
It   mixes   with   alcohol    in   all    proportions;    with   water 
only   to  about   one    tenth    the   weight   of  each.      It    is  a 
solvent  for  the  fats,  resins,  many   other   organic   bodies, 
and,  to  a  much  less  degree,  for  sulphur  and  phosphorus. 

Owing  to  its  ready  volatility  it  is  used  for  the  pro- 
duction of  cold,  but  its  use  requires  care,  as  its  vapor 
is  very  easily  set  on  fire,  and,  when  mixed  with  air, 
becomes  violently  explosive.  The  vapor  when  inhaled 
produces  complete  insensibility  to  pain,  and  is  the  chief 
anaesthetic  used  by  surgeons  in  the  United  States.  Swal- 
lowed, it  has  a  fiery  taste,  and,  even  in  small  doses, 
rapidly  brings  on  the  stupor  of  intoxication. 

749.  Methyl  ether,  CII8-O-CII8,  is  made  from  methyl 
alcohol  and  strong  sulphuric  acid.     It  is  a  colorless  gas, 
combustible,  condensed   by  a  cold  of  — 21°  to  a  liquid. 
Cold  water  absorbs   37    times   its  volume,  and   acquires 
thereby  the   taste   and   odor  of  the   ether.     It   is  meta- 
meric  with  ethyl  alcohol,  CH3-CH2OH. 

750.  Methyl-ethyl  ether,   CII3-  O  •  C2H5,  is  formed  by 
the    metathesis   of  sodium    ethylate   and    methyl    iodide. 
It  is  an  inflammable  liquid,  boiling  at  11°,  and   resem- 
bling ethyl  ether  in  most  other  particulars. 


THE  ETHERS.  401 

Three  ethers  are  known  which  are  metameric  with 
butyl  alcohol,  C4H10O,  and  six  with  amylic,  C5H12O. 

Allyl  alcohol,  C3H5OH,  has  also  its  ethers,  which  are  formed 
from  allyl  iodide,  C3H5I.  The  following  is  the  reaction  for  allyl 
ether,  2C3H5I+Ag2O  =  2AgI  +  (C3II5)2O.  It  is  a  colorless  liquid, 
boiling  at  82°.  It  is  thought  to  exist  free  in  the  crude  oil  of  garlic, 
together  with  the  ethereal  sulphide,  (C3H5)2S. 

Mixed  allyl  ethers  result  by  treating  these  with  sodium  alco- 
holates;  as,  e3H5IH-CH3ONa=NaI+C3H5  •  O  •  CH3,  yields  allyl- 
niethyl  ether.  The  general  behavior  of  these  compounds  is  quite 
analogous  to  those  previously  described. 

The  oxides  of  the  glycols  are  produced  by  the  action  of  caustic 
potash  upon  their  chlorhydrins;  as,  CH2C1  •  CH2OH  +  KOH  = 

KC1  -f  H2O  +  CH2     O  •  CH2  =  ethylene  oxide. 

Ethylene  oxide,  C2H4O,  is  a  liquid  of  pleasant  odor;  sp.  gr., 
.898;  boils  at  13.5°;  a  strong  base  combining  with  acids  to  form 
compound  ethylene  ethers. 

A  glyceryl  oxide  also  exists,  (C3H5)2O3,  which  remains  along 
with  allylin,  C3H5(OH)2  •  O  •  C3H5,  in  the  retorts  used  in  making 
allyl  alcohol  by  heating  glycerine  with  oxalic  acid. 

751.  Thio  ethers  may  be  obtained  by  heating  the  alkyl 
chlorides   with    an    alcoholic   solution    of  potassium   sul- 
phide and  distilling;  as, 

2C2H5C1  +  K2S  =  2KC1  +  (C2H5)2S  =  ethyl  sulphide. 

These  bodies  are  for  the  most  part  liquids,  easily  vola- 
tilized, and  of  an  offensive  odor,  which  is  frequently 
characteristic.  They  bear  the  same  relation  to  the  mer- 
captans  that  oxygen  ethers  do  to  the  alcohols. 

Allyl  sulphide,  (C3H5)2S,  is  the  most  interesting  of 
these,  as  it  is  the  principal  part  of  the  oil  obtained  by 
distilling  garlic  with  water.  It  is  formed  synthetically 
from  allyl  iodide,  2C3H5I-f  K2S^2KI-j-  (C3H5)2S. 

752,  Allyl  sulphocyanate,  C3H5-CNS,  is  obtained  (syn- 
thetically) from  the  reaction, 

C3H5I  +  KCNS  =  KI  +  C8H5-  CNS, 

Chem.— 26. 


402  ORGANIC  CHEMISTRY. 

and  also  from  black  mustard-seeds.  These  seeds  contain 
a  bland  oil,  which  may  be  removed  by  pressure.  (2) 
The  "oil-cake"  remaining  contains  potassium  myronate, 
and  a  natural  ferment  called  myrosin.  Vpon  the  addi- 
tion of  water,  a  fermentation  is  set  up,  and  the  potas- 
sium myronate  is  converted  into  glucose,  acid  potassium 
sulphate,  and  the  allyl  mustard-oil,  C10II18KNS2O10  = 
C6H12O6  -f  KIISO4  +  O8H5CXS.  The  mustard-oil  is 
then  distilled  by  the  aid  of  steam;  sp.  gr.,  1.02;  boils, 
150°C.  It  blisters  the  skin  quickly,  and  its  vapors  are 
exceedingly  pungent. 

The  term  "mustard-oils"  is  made  also  to  include  other 
isosulphocyanates  (as  C  2 II  5CNS  =  ethyl  sulphocyanate), 
which  have  some  of  the  properties  of  the  allyl-oil. 

Selenium  and  tellurium  also  act  as  "linking  elements"  between 
two  alkyl  radicals.  The  ethers  they  form  have  as  a  rule  exceed- 
ingly enduring  and  offensive  odors. 

753.  The  compound  ethers  are  ETHEREAL  SALTS,  which 
exactly  correspond  to  the  metallic  salts  of  the  oxy-acids. 
A  great  variety  of  these  compounds  are  known,  inas- 
much as  any  acid  radical  may  be  made  to  combine  with 
any  alkyl  radical  of  equal  valency  to  produce  them. 

Some  one  of  these  compounds  is  always  formed  when 
the  alcohols  and  strong  acids  are  mixed  together;  as, 
C2H5On  +  IIXO3^n2O-fC2II5-OXO2=ethyl  nitrate^ 
nitric  ether.  With  poly  basic  acids  several  ethereal  salts 
may  be  formed;  as,  C2II5,  H2PO4,  monethyl  phosphate; 
(C2H5).2IIPO4,  di-ethyl  phosphate,  which  are  ether  acids, 
and  (C2H5)3PO4,  tri-ethyl  phosphate,  which  is  a  neutral 
ether. 

All  compound  ethers  are  reconverted  by  heated  steam 
into  free  acid  and  free  alcohol;  or,  more  simply,  by 
boiling  with  a  strong  base,  like  caustic  soda  or  lime ; 
as,  C2H5-  0X0  2  +  NaOH  ==  XaXO3  -f  C2H5OH.  This 
process  is  known  as  saponification. 


THE  ETHERS.  403 

754,  The  nitric  ethers  are  prepared  in  small  quantities 
and  at  low  temperatures.     Ethyl  nitrate,  C2H5ONO2,  is 
obtained    by  distilling   60   grammes   of  alcohol   with   an 
equal  weight  of  strong  nitric  acid,  15  grammes  of  urea 
being  previously  added.     The  ether  is  nearly  insoluble 
in   water,   and    may  be   freed   from   the    alcohol,   which 
distils  over  with  it,  by  washing  with  water  and  rectify- 
ing  with    CaCl2.      It   is   a   colorless   liquid   of  agreeable 
odor;  sp.  gr.,  1.11;  boils  at  85°.     Its  vapor,  when  over- 
heated, is  explosive. 

Ethyl  nitrite,  C2H5ONO,  is  obtained  pure  by  passing 
the  vapors  of  nitrous  anhydride  into  alcohol,  kept  cool 
by  ice,  2C2H5OH  +  N2O3  =  H2O  +  2C2H5ONO.  It  is 
a  colorless  liquid,  having  the  odor  of  apples;  sp.  gr., 
0.95;  boils  at  16°;  soluble  in  40  parts  of  water.  The 
"sweet  spirits  of  nitre11  is  a  solution  of  ethyl  nitrite  in 
alcohol,  mixed  with  oxidation  products, — aldehyde,  acetic 
acid,  ethyl  acetate,  etc.,  which  are  sometimes  present  in 
sufficient  quantity  to  render  it  unfit  for  use. 

755.  It   has   already  been  noted   that   sulphuric  acid 
forms  two  series  of  ethereal  salts.     For  example:   ethyl 
sulphate,   (C2H5O)2SO2,   formed   by   passing   the   vapor 
of  SO3  into  well  cooled  anhydrous  ether,  and  sulphovinic 
or  ethyl   sulphuric   acid,  C2H5O  •  SO2-  OH,  which  is  an 
intermediate  product  in  the  manufacture  of  ether. 

This  may  be  isolated  (1)  by  digesting  a  mixture  of  three  mole- 
cules of  alcohol  with  one  of  the  strong  acid.  (2)  Diluting  the 
mixture  with  water  and  saturating  with  lead  carbonate.  (3)  Fil- 
tering off  the  lead  salt,  and  decomposing  it  with  H2S.  (4)  The 
free  acid  is  then  concentrated  to  an  acid  syrup ;  sp.  gr.,  1.3.  Un- 
like sulphuric  acid,  all  its  salts  are  soluble  in  water.  It  is  easily 
decomposed  on  heating,  and  if  heated  with  ethyl  alcohol  yields 
ethyl  ether ;  with,  other  alcohols,  the  mixed  ethers.  For  example : 
with  amyl  alcohol,  ethyl  amyl  ether, 

C2H50  •  S02  •  OH  -f  CgHn  •  OH  =  H2SO4  +  C2H5  •  O  •  C.H^. 


404  ORGANIC  CHEMISTRY. 

756.  Ethyl  sulphite,  C12H5O  •  SO  •  C'21I5O,  is  formed  by 
the  action  of  sulphur-di-'chloride  upon  alcohol;  as. 
3(C2H5OH)-f-S2Cl2r=2HCl-f  C,H5SH-f  (C2H5O)2SO. 

It  is  a  liquid  of  peppermint-like  odor;  sp.  gr.,  1. 08;  boils, 
100°.  No  acid  sulphites  corresponding  to  those  are 
known,  but  instead  of  them  an  important  series  of  iso- 
mers  which  may  be  considered  as  derived  from  an  un- 
symmetrical  sulphurous  acid,  II  •  SO.,-  Oil,  and  which 
take  the  name  of  N////>Ao/i/''  //<*///x.  The  sulphonic  acids 
may  be  formed  by  oxidi/ing  the  mercaptans;  as, 
C2II5SIIfO3  (i._,II.;S()2OI[^otliyl  sulphonic  acid,  or 
by  heating  the  haloid  ethers  with  potassium  sulphite;  as, 

c2n.r -i  K,SO.$:    KI  i  <',n5so,oK 

potassium  ethyl  sulphonate. 

These  acids  are  stable  compounds,  in  every  way  analo- 
gous to  the  carboxyl  acids.  Their  ethers  are  formed  by 
the  action  of  their  chlorides  upon  sodium  alcoholates;  as, 
CaH5-SO1-Cl-hC2H6ONa=NaCl+C2II5S6,-0-CaHfl= 
ethylic  ethyl-sulphonic  ether. 

757.  The  ethereal  salts  of  the  organic  acids  are  usually 
prepared  by  heating  the  respective  alcohols  with  a  mix- 
ture of  the  sodium  salt  of  the  acid  and  strong  sulphuric 
acid. 

Sulphuric  acid  is  commonly  used  in  the  manufacture  of  the 
oxygen  ethereal  salts;  partly  because  of  its  reactions  with  the  al- 
cohols, and  partly  because  it  serves  to  liberate  from  their  salts 
other  acids  that  they  may  act  in  a  nascent  state  upon  the  alcohols; 
as,  2(CH3COONa)  +  H2SO4  =  Na2SO4  +  2(CH,COOH). 

C3II602.  Methyl  acetate,  CII3  O  •  C2H3O,  occurs  in 
crude  wood  spirit;  sp.  gr.,  .956;  boils,  56°C.  Its  isomer, 
ethyl  formate,  C2H5-O-CHO,  is  prepared  by  digesting 
oxalic  acid,  glycerine,  and  alcohol  and  afterwards  distill- 
ing. It  is  a  liquid,  having  an  odor  recalling  that  of 
peach  kernels;  sp.  gr.3  .945;  boils,  54°C. 


THE  ETHERS.  405 

C4H8O2.  Ethyl  acetate,  C2H5-  O  •  C2H3O,  is  obtained 
by  distilling  one  part  of  alcohol  with  two  parts  of  so- 
dium acetate,  and  three  parts  of  sulphuric  acid.  The 
crude  product  is  washed  with  a  very  little  strong  brine, 
and  rectified  over  calcium  chloride.  It  is  a  colorless  liq- 
uid, of  an  agreeable  ethereal  odor;  sp.  gr.,  0.9;  boils,  73°; 
soluble  in  17  parts  of  water,  and  partially  decomposing  in 
it.  Its  metamers  are  propionic  formate,  C3H7-O-CHO; 
the  methyl  propionates,  CH3-  O  •  C3H5O;  and  the  butyric 
acids,  C3H7-COOH. 

758.  Many  of  the  ethereal  salts,  which  are  analogous 
to  these,  have  agreeable  odors,  which,  in  some  cases,  re- 
semble those  of  fruits  ;  ethyl  butyrate,  that  of  pine  ap- 
ples; isoamyl  acetate,  that  of  jargonelle  pears;  isoamyl 
isovalerate,  that  of  apples ;  ethyl  pelargonate,  that  of 
quinces.  Ethyl  cenanthate  is  thought  to  be  a  part  of 
the  aroma  of  old  wines. 

The  artificial  fruit  essences  are  mixtures  of  such  ethers,  with 
acetic  ether,  alcohol,  and  glycerine.  The  mixtures  used  in  the 
compounding  of  imitation  spirits  are  of  the  same  sort,  rum  essence 
contains  ethyl  formate,  etc.,  cognac  essence,  acetic  and  nitrous 
ethers,  etc.  Some  of  the  odoriferous  oils,  naturally  occurring  in 
plants  and  in  animals,  are  also  ethereal  salts,  as  the  oil  of  winter- 
green  is,  CH3  •  O  •  C7H5O2  =  methyl  salicylate.  Such  are  also 
spermaceti  and  the  chief  constituents  of  bees-wax. 

The  ethereal  salts  of  polyvalent  radicals  (acid  as  well  as  alkyl) 
are  of  almost  infinite  variety.  The  oxygen  ethers  of  carbonic  acid 
should  be  two;  as,  ethyl  carbonate,  C2H5O  •  CO  •  OC2H5,  obtained 
by  metathesis  of  silver  carbonate  and  ethyl  iodide,  and  acid  ethyl 
carbonate,  C2H5O  •  CO  •  OH,  which  is  known  only  in  its  salts, 
such  as  ethyl  potassium  carbonate.  C2H5O  •  CO  •  OK,  obtained  by 
passing  carbonic  anhydride  into  an  alcoholic  solution  of  caustic 
potash.  The  fats  are  salts  of  glycerol,  $  646. 

Thio -carbonic  ethers  are  formed  from  the  alkyl  iodides 
by  the  action  of  the  alkaline  sulpho-carbonates ;  as, 
2C2H5I  +  K2S,  CS2  =  2K1  -f  (C2H5S)2CS  =  ethyl  sul- 
pho-carbonate. 


406  ORGANIC  CHEMISTRY. 

The  best  known  of  the  acid  thio  ethers  are  the  xan- 
thates,  which  are  ethyl  di- thio -carbonates.  Potassium 
xanthate  is  prepared  by  mixing  a  saturated  solution  of 
caustic  potash  in  hot  alcohol  with  carbon  bisulphide, 
CS2  +  KIIO  +  CjHfiOH  =  =  H20  +  C2II5  •  O  •  CS  •  SK, 
which  separates  out  on  cooling  jn  beautiful  silky  needles; 
sp.  gr.,  1.56.  These  must  be  quickly  dried  and  kept  out 
of  contact  with  the  air.  It  is  a  very  delicate  test  for 
cupric  salts,  which  yield,  with  it  in  aqueous  solutions, 
yellow  cuprous  xanthate  (02II6O  •  CS  •  S)2Cu2". 

Potassium  xanthate,  when  decomposed  by  cold  dilute  sulphuric 
acid,  yields  xanthic  acid,  C2H5O  •  CS  •  SII,  a  colorless,  oily  liquid, 
heavier  than  water,  and  decomposed  at  24°  into  alcohol  and  car- 
bonic bisulphide.  It  is  proposed  to  use  this  body,  and  some  of  its 
comjKiunds  in  place  of  CS2  f°r  destroying  insects  on  plants  and  in 
grain.  Like  any  other  acid,  it  has  its  metallic  salts,  ethers,  etc., 
C2H5()  CS  •  SC2H5  =  xanthic  ether,  amides,  C2II5O  •  CS  •  NII2  = 
xanthamide,  and  other  derivatives. 

The  thio  compounds  of  other  alcohol  radicals,  as  far  as  known, 
agree  with  those  described. 

759.  The  normal  oxalic  ethers  are  prepared  by  digest- 
ing oxalic  acid  with  the  anhydrous  alcohols,  and  after- 
wards distilling.  The  acid  ethers  are  little  known  in  the 
free  state. 

Ethyl  oxalatc,  C2TI5O  •  CO  •  CO  •  OC2H5,  is  a  colorless  liquid,  of 
faint  odor;  sp.gr.,  1.08;  boils,  186°.  It  is  very  easily  decomposed, 
and  is  converted  by  dry  gaseous  ammonia  into  ethyl  oxamate, 
C2H5O  •  CO  •  CONH2,  and  by  aqueous  ammonia  into  oxamide, 
NH2CO  •  CONH2,  and  alcohol. 

The  polyhydric  acids  are  capable  of  forming  ethers  by  the  sub- 
stitution of  an  alkyl  radical  for  their  replaceable  hydrogen.  If 
their  basic  hydrogen  be  wholly  replaced,  they  yield  normal  ethereal 
salts;  and  if  partially  replaced,  acid  salts,  as  illustrated  by  those  of 
tartaric  acid  on  the  next  page.  If  the  normal  salts  are  treated 
with  the  chlorides  of  acid  radicals,  even  the  alcoholic  hydrogen 
may  be  replaced  by  such  acid  radicals,  as  in  ethyl  di-acetotartrate, 
(CH)2(OC2H30)2(COC2H5)2. 


THE  ETHERS.  407 

COOH  COOC2H5  COOC2H5 

CHOH  CHOH  CHOH. 

I  I  I 

CHOH  CHOH  CHOH. 

I  I  I 

COOH  COOH  COOC2H5. 

Tartaric  acid.  Acid  ethyl  tartrate.  Normal  ethyl  tartrate. 

So  also  the  amid -acids  have  their  ethers,  as  the  ethyl  amid-acetate, 
CH2NH2  •  COOC2H5,  obtained  from  glycocine. 

Enough  has  been  given  to  illustrate  the  wonderful  flex- 
ibility of  organic  compounds,  and  to  indicate  the  meth- 
ods by  which  they  are  obtained  and  classified.  Each 
radical  has,  so  to  speak,  its  own  personality,  and,  so 
long  as  it  exists  entire,  plays  a  definite  part  in  the 
various  compounds  into  which  it  enters.  When,  how- 
ever, it  is  modified  by  becoming  chlorinated,  oxidized, 
etc.,  it  forms  a  new  group  with  new  functions.  The 
ethers  are  the  best  illustrations  of  these  growths  and 
transformations. 

760.  The  lecithins  are  a  group  of  complex  ethers  of 
glycerol,  found  in  the  cell  substance  of  maize,  brain 
substance,  egg,  albumin,  etc.  They  are  fats  containing 
the  radicals  of  two  fatty  acids,  glycerol,  phosphoric  acid, 
and  the  ammonium  hydroxide,  neurine  (p.  386).  The 
brain  substance  probably  contains  palmitic-oleic  lecithin. 

CH2-0-C16H310. 
CH  -0-C18H330. 

CH2-  O  •  PO  •  OH. 

6  •  (C2H4)N(CH3)3OH. 


408  ORGANIC   CHEMISTRY. 


Recapitulation. 

(1)  The  ethers  are  volatile,  inflammable  compounds  of  character- 
istic odors. 

(2)  Each  contains  at  least  one  alkyl  radical  united  to  a  negative 
radical,  like  I',  or  O",  or  P///. 

(3)  Haloid  ethers  contain  only  one  alkyl  radical. 

(4)  Simple    ethers   contain    two    or    more    similar    alkyl    radicals 
united  by  O,  by  8,  etc. 

(5)  Mixed  ethers  contain  two  or  more  dissimilar  alkyl  radicals. 

(6)  Compound    ethers   contain    an    acid    radical,    and    are    ethereal 
salts. 

(7)  These  ethers  are   easily  broken   up,  and   are,  therefore,  useful 
in  chemical  synthesis. 

(8)  The  conversion  of    the  ethereal   salts   into    their  alcohols   and 
acids  is  known  JIK  snponificution.     It  may  be  accomplished  by 
heating  «with  steam,  with  alkalies,  and  with  acids. 

(9)  The  hydrins  are  ethers  formed   from    polyhydric   alcohols   by 
the  substitution  of  negative  radicals  for  a  part  or  the  whole 
of  their  hydroxyl. 

(10)  The  compounds    of   nitrogen,  with   alkyl   radicals,  are  of  two 
sorts;   ethereal  salts,  like   the  nitric  and    nitrous  ethers;  and 
the    nitro   derivatives,  which    yield    amines    with    nascent  hy- 
drogen. 

(11)  The  cyanogen  compounds   are  also  two,  —  cyanides    and    iso- 
e  vanities. 


CHAPTEE    XXVI. 

THE    AROMATIC    HYDROCARBONS. 

761,  The  aromatic  hydrocarbons  may  be  regarded  as 
derived  from  BENZENE,  C6H6,  by  successive  additions  of 
CH2,  or  by  conjugation  of  two  or  more  benzene  mole- 
cules.     The    six    hydrogen    atoms  of  benzene  may,  one 
after  the  other,  be  replaced  by  monovalent  radicals,  like 
Cl,  OH,  COOH.     It  is  noticeable  that  the  "  nitro,"  NO2, 
substitution   takes   place  more   readily  than   is  the   case 
with  the  fatty  derivatives,  generally  by  direct  action  of 
strong  nitric  acid,  and  not  requiring  the  previous  forma- 
tion  of  chlorides,    etc. ;    and   also  that   strong   sulphuric 
acid  readily  forms  with  them   the   sulphonic  acids,  con- 
taining the   group   SO2OH,  and   that  these   two  classes 
of  derivatives  are  of  much  greater  importance  than  the 
analogous  compounds  in  the  fatty  series. 

Although  most  of  the  derivatives  known  contain  one, 
two,  or  three  substitutions  of  hydrogen,  it  appears  that 
all  of  the  hydrogen  atoms  in  benzene  have  the  same 
value,  as  if  the  empirical  formula  of  benzene  were  (CH)6. 
Consequently,  substances  like  C6H5C1  or  C6H5NO2,  in 
which  only  a  single  hydrogen  atom  has  been  replaced 
by  a  monovalent  radical,  can  have  no  true  isomers;  their 
metamers,  if  any,  must  come  from  the  fatty  series. 

762.  These  facts  have  led  to  the  theory  that  in  the 
benzene  group,  C6H6,  (1)  the  six  carbon  atoms,  which 
constitute    the  "benzene    nucleus,"   are   so   united   as   to 
form   a  "  closed   chain,"  and   to   leave   one  valency   free 
for  each.     (2)  That  this  valency  is  satisfied  in  benzene 


410  ORGANIC  CHEMISTRY. 

by  hydrogen;  (3)  that  "substitution  products"  are 
formed  by  the  replacement  of  these  hydrogen  atoms  by 
other  radicals.  These  notions  find  expression  in  the 
diagrams  already  given  on  page  289,  or  more  simply  by 
a  hexagon  with  angles  numbered  to  represent  the  places 
of  the  six  CII  groups,  or  their  substitution  products: 


NO, 


HC 


Cf)JI,;,  benzene.  C6II5NO2,  nitro- benzene. 

(4)  A  very  few  "addition  products"  are  known,  as 
C61I61I6  and  C6II6CM6.  In  such  compounds  each  car- 
bon atom  must  act  divalent,  and  consequently  the  chain 
must  be  unlocked. 


CH 


HC 


Benzene.  Hexa-hydro-benzene. 

763.  Compounds  formed  by  the  substitution  of  two  or 
more  hydrogen  atoms  exhibit,  in  a  marked  degree,  the 
isomerism  which  is  due  to  the  position  or  orientation  of 
the  substituted  radicals.  There  are  three  cases  of  such 
isomerism  due  to  two  substitutions:  (1)  Ortho  derivatives 
are  formed  by  consecutive  substitution,  displacing  neigh- 
boring carbon  atoms,  as  1:2  or  2:3,  etc.  (2)  Meta  de- 
rivatives, by  substitutions  separated  by  a  single  hydrogen 


THE  AROMATIC  HYDROCARBONS.  411 

atom,  as  1:3  or  1:5.     (3)  Para  derivatives,  by  substitu- 
tion as  widely  separated  as  possible ;  viz,  1:4: 


Ortho.  Meta.  Para. 

Three  isomers  are  also  possible  when  the  same  rad- 
icals are  substituted  three  or  four  times  for  as  many  hy- 
drogen atomy.  These  are  designated  as 


Consecutive.        Symmetrical.        Unsymmetrical. 

according  to  the  positions  which  the  substituted  radicals 
take,  as  illustrated  by  the  diagrams. 

The  position  which  is  assigned  to  any  group  is  deter- 
mined by  the  compounds  into  which  it  enters,  or  from 
which  it  may  be  derived.  A  para  compound  can  come 
only  from  an  unsymmetrical  tri-derivative ;  an  ortho  from 
either  an  unsymmetrical  or  consecutive  tri-derivative, 
and  a  meta  from  any  one  of  the  three  tri -derivatives. 
Hence,  this  rule.  • 

The  di-derivatives  of  benzene  are  termed  para  (1:4), 
ortho  (1:2),  and  meta  (1:3),  according  as  they  may  be 
formed  from  or  give  rise  to  one,  or  two,  or  three  tri-deriv- 
atives. 


412 


ORGANIC  CHEMISTRY. 


764.  When  the  substituted  radicals  are  different,  the 
number  of  isomers  is  greatly  increased,  and  also  the  dif- 
ficulty of  establishing  their  orientation. 

For  example,  the  trivalent,  C6H3,  is  the  nucleus  for  three  tri- 
brom  derivatives,  C0H3Br3 ;  viz, 


Consecutive.  Symmetrical.  Unsymmetrical. 

Now,  if  one  of  these  be  replaced  by  the  radical  nitryl,  NO2,  six 
isomers  of  nitro-di-brom  benzene,  CcII3Br2NO2,  become  possible; 
viz, 


NOi 


Yielding  ortho  di-brom     Yielding  meta  di-brom  Yielding  para 

benzene.  benzene.  di-brom  benzene. 


765.  Another  kind  of  isomerism  is  caused  by  parallel 
substitutions;    one   in    the   nucleus,  and   another   in   the 


THE  AROMATIC  HYDROCARBONS. 


413 


lateral   chain.     The   three   cresols,  C6H4-OH,  CH3J  are 
metameric  with  benzyl  alcohol.  C6H5-  CH2OH. 


OH 


OH 


CH 


OH 


CH2OH 


CH 


Ortho. 


Meta. 


Cresols,  C7H8O. 


CH3 

Para-  Primary 

Benzyl  alcohol,  C7H8O. 


Similarly,  chlorine,  when  passed  into  boiling  toluene,  CftH5  •  CH3, 
produces  a  series  of  chlorides,  which  are  very  like  the  chlorides  of 
the  alcohols.  This  substitution  is  supposed  to  take  place  in  the 
lateral  chain,  as  benzyl  chloride,  C6H5  •  CH2C1;  benzyl  di-chloride, 
C6H5  •  CHC12,  and  benzyl  chloroform,  C6H5  •  CC13. 

Very  different  compounds  are  formed  when  the  reaction  takes 
place  in  the  cold  or  in  the  presence  of  iodine,  the  substitution  then 
taking  place  in  the  nucleus,  as  chlor-toluene,  C6H4C1  •  CH3 ;  di- 
chlor- toluene,  C6H3C12  •  CH3,  etc.,  to  C6C15  •  CH3,  and  there  are 
also  chlorides  containing  both  kinds  of  substitutions;  as, 

C6H4C1  •  CH2C1  =  chlor-benzyl  chloride, 

metameric  with   the   other  two  di-chlorides.     Altogether,  there  are 
nearly  a  hundred  chlorides  between  C6H5  •  CH3  and  C6C15  •  CC13. 

766.  Many  of  the  aromatic  hydrocarbons  are  obtained 
by  the  fractional  distillation  of  coal-tar,  which  is  a  bye- 
product  in  the  manufacture  of  illuminating  gas.  The 
first  portion  (about  10^  of  the  tar)  is  light  oil,  which 
is  a  mixture  of  hydrocarbons  lighter  than  water,  as  ben- 
zene, toluene,  etc.  The  second  portion  (about  25%)  is 
the  heavy  or  dead  oil  which  contains  the  phenols,  the 
amine  bases,  and  naphthaline.  (3)  If  the  pitch  which 


414 


ORGANIC  CHEMISTRY. 


remains  is  further  distilled,  solid  hydrocarbons,  like  an- 
thracene and  chrysene,  pass  over;  and  (4),  there  remains 
as  a  tinal  product  only  a  residue  of  coke. 


787.  The  benzene  radical.,  (C6H5/,  (C.II4)",  ( 
etc.,  by  their  union  with  other  radicals,  form  series  of  hy- 
drocarbons, chlorides,  alcohols,  aldehydes,  acids,  amines, 
etc.,  which  resemble  those  of  the  paraffins,  besides  a  few 
which  are  unique.  Among  the  latter  are  the  phenols, 
so  named  from  the  first  member,  C6H5OII,  commonly 
known  as  carbolic  acid;  the  quinones  are  a  sort  of  per- 
oxides, as  (C6I14)"O2,  containing  the  diatomic  radical 
O2  ;  and  there  are  also  udiazo"  compounds,  containing 
the  double  nitrogen  group,  __^N-N=-  or  —  N:N  —  . 

768.  Some  benzene  hydrocarbons,  Cnll,,n_6. 
Containing:  Containing: 


(C6H6)'. 


C6H6,  benzene. 

C7II8,  toluene,  or  methyl  benzene. 

C8H10,  ethyl  benzene. 

^9^x2,  propyl  benzene, 
cumene  (isopropyl). 


C10H14,  isobutyl  benzene. 

CnHjg,  isoamyl  benzene. 
C12H18,  isohexyl  benzene. 

Benzole  acid, 


(C6HJ"(C6H8r'(C6H,)'%  etc. 
Each  with  3  isomers  (o.  m.  p.), 
etc. 


C6H4(CH3)2,  xylene. 

Ethyl  methyl  benzene, 
pseiido-cumene,  and 
mesitylene,  C6H3(CH3)3. 

C6H4     CH3,  C3H7,  cymene,  etc., 
ethyl  dimethyl  benzene, 

durene,  C6H2(CH3)4. 

Laurene,  metbyl  diethyl  benzene, 
C6H(CH3)5,  and  many  others. 

Hexa  methyl  benzene,  C(CH3)6. 


Yield,  on  complete  oxidation, 

|  Ortho,  meta,  and  para  acids. 


THE  AROMATIC  HYDROCARBONS.  415 

769.  Benzene,  C6H6,  is  manufactured  on  the  large  scale 
by  redistilling  the  light  oil  of  tar,  and   collecting  apart 
the    portion   which    boils    below   90°.     This   is    agitated 
with  strong  H2SO4,  washed  with  water  and  again  dis- 
tilled.    This  distillate  is  cooled  to  — 12°,  when  the  ben- 
zene crystallizes    out,   and    is   freed    from    the    adhering 
liquid  homologues  by  pressure.     It  may  also  be  obtained 
pure  by  distilling  benzoic  acid,  or  its  salts,  with  quick- 
lime, C6H5COOH-f  CaO  =  CaOC02-f  C6H6. 

Pure  benzene  is,  at  ordinary  temperatures,  a  bright, 
colorless  liquid,  of  peculiar  ethereal  odor;  sp.  gr.,  0.9; 
boils,  80.5°.  It  is  readily  volatilized,  and  burns  in  the 
air  with  a  luminous,  but  smoky  flame.  It  solidifies  at 
0°  to  a  mass  of  fern -like  crystals,  which  melt  again  at 
about  5°C. 

It  is  used  as  a  solvent  for  the  fats,  resins,  caoutchouc, 
and  also  dissolves  phosphorus  and  sulphur.  Its  prin- 
cipal use  in  the  arts  is  as  the  starting-point  in  the 
manufacture  of  the  aniline  colors. 

Di-phenyl,  C6H5  •  C6H5,  is  formed  when  benzene  vapor  is  passed 
through  red-hot  tubes. 

770.  The  hydrocarbons  homologous  with   benzene,  in- 
crease by  CH2,  and  are  formed  by  substituting  methyl, 
or  some  other  monovalent  alkyl  radical,  in  place  of  hy- 
drogen atoms.     Those  that  contain  the  univalent  radical 
phenyl,   C6H5,  as   toluene,  ethyl  benzene,  and   cumene, 
are    the   true    homologues   of  benzene,   and   resemble   it 
closely,  but  have  higher  boiling  and  solidifying  points. 
All   these  are   oxidized   by  chromic   mixture  to    benzoic 
acid,  C6H5COOH,  plus  other  products  dependent  on  the 
constitution  of  the  alkyl  radical.     Toluene  is  one  of  the 
products  of  the  distillation  of  tolu  balsam.     Cumene  and 


NOTE.  —  Benzene  is  sometimes  called  benzol  and  benzine;  the  termina- 
tion "ol"  is  reserved  for  the  alcohols;  the  lighter  paraffins  are  also  called 
benzene. 


416  ORGANIC  CHEMISTRY. 

cymene,  occur  in  certain  fragrant  oils,  as  cumin  and  cara- 
way. All  of  these  may  be  formed  synthetically  by  the 
action  of  sodium  upon  a  mixture  of  two  mono-haloids, 
which  contain  the  required  benzene  and  alkyl  radicals; 
as,  Na2-[-C6H5Br-fC2H5I=NaI-f-XaBr-^C6II5C2H5= 
ethyl  benzene. 

The  several  metarneric  series  which  contain  (C6II4)"f  (Cgll.,)'", 
and  (C6H2)I%,  may  be  produced  by  analogous  reactions,  but  often 
more  conveniently  by  decomposing  their  respective  acids  with 
quicklime.  Each  of  these  should  have,  by  theory,  its  three  iso- 
mers,— ortlio,  para,  and  meta,  etc.,— and  each  of  the  latter  its  own 
system  of  derivatives.  Among  these  are  to  be  noted : 

I.  The    rylenes,    C4II4(CII3)2,    so-called    because    they    are    also 
found    in    wood-tar.     They   yield,   by    partial    oxidation,  ortho-toluic, 
meta-toluic,  and  para-tolinc  acids,  CII3  •  C6II4  •  COOII   (metamers  of 
alpha-toluic  acid,  Cf(IL,     CII2  •  COOII);   and    (2),   by  complete  oxi- 
dation   the    bi-basic   acids,  C f,II4 (COOII) 2 ;    viz,   phthalic  (ortho),  iso~ 
phthalic   (meta),   and    tere-phthatic   (para).     Phthalic    acid    is    usually 
obtained  by  oxidizing  naphthalene. 

II.  The  trimethyl  benzenes,  C6II3(CII3)3,  are  all   found  in  the 
coal-tar   oils  which    boil    between    160°  and    170°;    viz,    mesitylene 
(1,  3,  5),  pseudo-cumene  (1,  3,  4),  and  the  consecutive  modification 
(1,  2,  3),  not  yet  obtained  pure.     Mesitylene  is  also  obtained  from 
acetone,  3(CII3     CO     CII3)  —  3H2()  =  C9II,  2.     When  oxidized  by 
dilute  nitric  acid, it  yields  (1)  mesitylenic  acid  (CII3)2C6H3COOII; 
(2)  mesidic  or  uvitic   acid,  CII3  •  C6II3     (COOII)2;   and  (3),  tri- 
mesic  acid,  C6H3 (COOII )3. 

III.  Fourteen  hydrocarbons,  C10H14,  are  already  known.     Spe- 
cial   interest    attaches  to   cymene,  because  it    may  be   formed    from 
the  terpenes,  Ci0H16,  such  as  oil  of  orange,  and  because  it  may  be 
obtained  by  heating  camphor  with  P2S5,  and  also  from  cumic  acid, 
C3H7     C6H4     COOH.     It  boils  at  175°;   sp.  gr.,  0.87;   oxidizes  to 
para-toluic  and  to  tere-phthalic  acids,  and  is,  therefore,  para  methyl 
propyl  benzene,  C3H7  •  C6H4  •  CH3. 

771.  Other  hydrocarbons.  Twenty-two  different  series 
of  hydrocarbons  have  been  partially  investigated,  reach- 
ing from  CnH2n+2  to  C^H.^.^.  Those  remaining  to  be  de- 
scribed, and  whose  constitution  is  known,  may  be  re- 
ferred to  complex  nuclei,  which  contain  (1)  benzene 


OTITEE  HYDROCARBONS. 


417 


radicals  united  to  those  of  the  olefines,  etc. ;  (2)  benzene 
radicals  united  together  ;  or  (3),  mixtures  of  these  two 
types.  Most  of  these  have  been  formed  synthetically; 
a  great  number — balsams,  resins,  etc.  —  have  been  found 
in  the  exudations  of  trees,  and  among  the  products  of 
destructive  distillation. 

772.  The  important  member  of  the  series,  CnH2n_8,  is 
styrolene  or  cinnamene,  C6H5  •  CH  :  CH2,  which  is 
ethenyl-benzene.  It  may  be  obtained  by  distilling  storax 
with  water,  or  cinnamic  acid  with  lime.  It  is  a  thin, 
oily  liquid,  of  aromatic  odor  (sp.  gr.,  0.924 ;  boils  at 
145°),  which  changes  on  keeping  to  a  solid  polymer, 
called  meta-styrolene. 

Acetenyl  benzene,  C6H5-  C  •  CH,  the  only  known  mem- 
ber of  the  series,  CnH2n_10,  resembles  acetylene. 


The  remaining  hydrocarbons  contain  two  or  more  benzene  groups; 


as, 


CH 


CnH2n_i2,  as,  Naphthalene;  C10H8,  or  C6H4  •  C4H4. 


CH 


CnH3H-i4;  as,  Di-phenyl,  C12H10,  or  C6H5  •  C6H5. 

Chem.— 27. 


418 


ORGAXIC  CHEMISTRY. 


CH 


CnII2n-ifi;  as,  Stilbene,  C14H12. 


Cnll-2n— 1»,  »*S  Anthracene,  f' 


CnHjn-24;  as,  Chrvscne,  C,  JF12. 

773.  Naphthalene,  riollg,  is  produced  when  the  vapors 
of  most  other  hydrocarbons  are  strongly  heated.  Ac- 
cordingly, it  is  a  bye  product  in  the  manufacture  of  coal- 
gas,  and  may  be  obtained  in  large  quantities  from  the 
coal-tar  which  distils  between  150°  and  220°.  It  forms 
in  white  rhombic  plates,  of  faint  odor  and  burning  taste, 
which  melt  at  79°C,  and  boil  at  218°  ;  sp.  gr.,  1.14.  It 
is  soluble  in  alcohol  and  ether. 

It  resembles  benzene  in  its  chemical  properties,  but 
has  a  much  greater  number  of  isomeric  substitution  prod- 


OTHER  HYDROCARBONS.  419 

ucts.  It  unites  directly  with  chlorine,  forming  first  ad- 
ditive products,  like  C10H8C12,  and  C10H8C14.  Also, 
after  distilling  these  chlorides  with  KHO,  substitution 
products,  as  monochlor  naphthalene,  C10H7C1,  which  has 
two  isomers;  di-chlor  naphthalene,  C10H6C12,  which  has 
ten  isomers,  etc.,  etc.,  to  perchlor  napthalene,  C10C18. 

Nitric  acid  produces  similar  substitution  products,  as 
C10H7NO2,  and  also  oxidizes  it  to  ortho-phthalic  and  ox- 
alic acids,  C10H8  +  O2=(COOH)2-f  (C6H4)(COOH)2= 
phthalic  acid.  (Page  444.) 

774.  Anthracene  and  phenanthrene,  C14H10,  are  ob- 
tained on  the  large  scale  from  that  portion  of  coal-tar 
which  distils  between  340°  and  400°.  They  resemble 
each  other  in  forming  colorless  tablets  with  a  fine,  blue 
fluorescence.  Phenanthrene  has  a  lower  melting  point 
(100°),  and  is  separated  from  its  isomer  by  its  greater 
solubility  in  boiling  alcohol.  Anthracene  melts  at  213° 
and  is  somewhat  soluble  in  warm  benzene. 

Anthracene  has  recently  attained  commercial  importance  as  the 
source  from  which  alizarin,  the  coloring  principle  of  the  madder- 
root,  may  be  artificially  produced  (1)  by  oxidizing  the  anthracene 
to  anthraquinone,  C6H4(CO)2C6H4 ;  (2)  this  becomes  anthraqui- 
none  di-sulphonic  acid  when  treated  with  strong  sulphuric  acid, 
C14H6O2(SO2OH)2.  (3)  The  product  fused  with  potash  changes 
to  potassium  alizarine,  C14H6O2(OK)2.  (4)  The  fused  mass  is  dis- 
solved in  water,  from  which  HC1  precipitates  alizarine,  which  is 
di-hydroxy-anthraquinone,  C6H4(CO)2C6H2(OH)2. 

Alizarine  crystallizes  in  yellowish-red  prisms,  which  may  be 
sublimed  at  290°  into  long  red  needles.  It  may  be  reduced  to 
anthracene  by  heating  with  zinc  dust,  or  be  oxidized  by  nitrous 
acid  to  anthraquinone  and  to  phthalic  acid.  It  is  a  weak  bibasic 
acid,  soluble  in  alkalies,  with  a  violet  color. 

From  this  solution  the  "madder  lakes"  of  the  dyer  are  prepared 
(with  lime  salts,  a  blue;  with  iron,  violet;  with  alum,  a  fine  red). 
The  famous  "Turkey  red"  is  due  to  an  alum  lake  treated  with  oil. 

Alizarine  was  formerly  produced  by  fermenting  the  madder- 
root,  which  contains  a  glucoside,  ruberythic  acid,  C26H28O14  = 
(C14H8O4  -f  2C6H12O6  —  2H20).  Old  madder-root  contains  also 


420  ORGANIC  CHEMISTRY. 

purpurine,  C14H5O2(OH)V  Madder-root,  when  boiled  with  dilute 
sulphuric  acid,  yields  a  mixture  of  alizarine  and  purpurine,  which 
is  known  as  yarancine. 

775.  Pyrene,  C16II10,  and   chrysene,   018H12,  are  the 
last  distillation  products  of  coal-tar.     Among  other  bodies 
of  this   group   are   retene,   C18H18,  found   fossil   and    in 
pine-tar,   and    the    fossil    resins    ozocerite,  ficht elite,    and 
asphaltum. 

TERPENES  AND  RESINS. 

776.  Among  the  natural   secretions   of  many  tropical 
plants   and    of  the    coniferous   trees,    are   a    number   of 
odorous   substances    which    are    known    in    commerce   as 
essential  oils,  turpentines,  balsams,  and  resins.     Most  of 
them    are    mixtures    which   contain    bodies   belonging   to 
different  chemical  groups.     Some  of  the  "essential  oils" 
contain   acids,  as   pelargonic  acid ;   many   are   ethers,  as 
the   oil   of  wintergreen  ;    some   aldehydes,  as  the   oil   of 
bitter  almonds;  some  phenols,  as  thymol;  and  some  are 
sulphur-oils,  as  the  mustard-oils;  but  a  very  large  num- 
ber consist  chiefly  of  hydrocarbons  polymeric  with  C5IIg. 
These  are  roughly  grouped   by  differences  in  their  boil- 
ing points. 

777.  Those   that   distil   between    160°-170°  are  called 
the   terpenes,  C101I16.     An   unusual    number  of  isomers 
(32)    having   this  empirical   formula  are  known.      They 
agree   in   almost   all   of  their  properties,  —  chemical  and 
physical, — but  differ  in  odor,  and  sometimes  also  in  their 
relations  to  polarized  light.     Among  these  are  the  vola- 
tile  oils  of  orange,  neroli,  lemon,  lime,  and  bergamotte, 
from   the  genus   citrus;   the  volatile  oils  of  beech,  cara- 
way, camomile,  coriander,  elemi,  juniper,  laurel,  parsley, 
pepper,  savin,  and  thyme.     The  oils  of  rose  and  cubebs, 
and  that  in  balsam  of  copavia,  are  polymers  of  C5H8. 


TERPENES  AND  RESINS.  421 

778.  These  volatile  or  essential  oils  are  obtained  from 
flowers,  fruits,  and  other  parts  of  plants  by  pressure  or 
by  distillation  with  water. 

They  have  a  pungent  odor  and  taste,  and  produce  upon  paper 
a  greasy  stain,  which  soon  disappears.  In  their  chemical  actions, 
they  behave  like  turpentine.  The  crude  turpentines  are  seini-fluid 
balsams,  which  exude  from  incisions  made  in  the  bark  of  various 
species  of  pines,  larches,  and  firs.  The  principal  varieties  are  the 
North  Carolina,  the  Bordeaux,  the  Venice  turpentines,  and  Canada 
balsam.  When  these  are  distilled,  either  alone  or  with  water,  they 
yield  the  volatile  oil  of  turpentine,  and  leave  behind  a  solid  resin, 
colophony.  The  oils  of  turpentine  are  mixtures  of  several  isomers 
of  terebenthine,  C10H16,  which  turns  the  plane  of  polarization  to  the 
left,  and  of  australene,  C10H16, which  is  dextro-rotatory. 

The  purified  oils  of  turpentine  are  thin  colorless  liq- 
uids, of  a  somewhat  disagreeable  odor;  specific  gravity, 
0.87  ;  boil  at  161°.  They  are  nearly  insoluble  in  water, 
but  are  freely  miscible  with  alcohol  and  ether.  They 
are  solvents  of  the  fixed  oils  and  the  resins,  and  are 
largely  used  in  making  paints  and  varnishes. 

When  exposed  to  the  air,  turpentine  rapidly  absorbs  oxygen, 
which  it  again  yields  in  the  form  of  hydrogen  peroxide  on  being 
warmed  with  water.  Chlorine,  bromine,  and  iodine  act  energetically 
upon  it.  In  most  cases  two  isomeric  compounds  are  produced,  one 
solid  and  the  other  liquid.  The  solid  hydrochloride,  C10H16HC1, 
has  the  odor  of  camphor.  Strong  nitric  acid  decomposes  it  with 
great  violence. 

779.  The  camphors  are  very  nearly  related  to  the  ter- 
penes,  and  appear  to  be  the  solid  products  of  their  oxi- 
dation.    Common    or   laurel   camphor,   C10H16O,   is   ob- 
tained   from    the    camphor-tree    of  Japan.      This   or   its 
isomer  has  been  produced   artificially  from  cymene.     It 
is  a  tough,  translucent  mass,  a  very  little   lighter  than 
water   (0.98),   of  peculiar  taste   and   odor.     It   sublimes 
at  ordinary   temperatures,  fuses   at   175°,  and   distils  at 
204°. 


422  ORGANIC  CHEMISTRY. 

It  is  largely  used  as  a  destroyer  of  moths,  and  as  a  household 
medicine.  It  is  but  slightly  soluble  in  water,  but  readily  in  al- 
cohol and  the  essential  oils.  When  heated  in  alcoholic  solution 
with  caustic  potash,  it  is  decomposed  into  borneol  and  camphic 
acid,  C10II15O  OH. 

Borneol,  or  Borneo  camphor,  C10H17OII,  strongly  re- 
sembles laurel  camphor,  but  has  a  more  peppery  taste 
and  odor.  It  may  be  converted  into  laurel  camphor  by 
nitric  acid.  Both  these  camphors  yield,  by  abstraction 
of  water,  rytncne,  C10ir,4,  and  other  hydrocarbons. 

Menthol,  C10H20O,  occurs  in  the  oil  of  peppermint, 
and  yields,  by  abstraction  of  H2O,  menthene,  C10IIlg. 

780.  The  balsams  are  mixtures  of  the  volatile  oils  and 
the  resins.    When  first  obtained,  they  are  generally  thick 
liquids,   but   gradually    harden   on    exposure   to   the   air. 
Besides    the    crude    turpentines    already    mentioned,  are 
others,  which  contain,  in  addition,  benzole  and  cinnamic 
acids,  as  Peru  and  tolu  balsams,  storax  and  gum  benzoin. 

The  resins  are  brittle  amorphous  bodies,  which  are  in- 
soluble in  water,  but  are  soluble  in  alcohol  and  in  the 
volatile  oils.  Common  resin,  or  colophony,  is  a  good  ex- 
ample. Most  of  them  are  mixtures,  containing  various 
acids  ;  colophony  containing  two  isomers,  sylvic  and 
pimaric  acids,  C20II30O2. 

Copal,  sandarac,  dragon's  blood,  mastic,  and  lac  are  used  ex- 
tensively in  varnishes.  The  lac  results  from  the  sting  of  an  insect 
upon  certain  East  Indian  trees.  While  in  its  crude  state,  it  is 
called  stick-lac,  or  seed-lac,  and  contains  a  red  dye,  which  is  due 
to  the  insects.  When  purified,  it  forms  the  well  known  shellac, 
the  chief  ingredient  of  good  sealing-wax.  Amber  is  a  fossil  resin, 
yielding,  on  distillation,  amber  oil,  succinic  acid,  and  two  resins. 

781.  The  gum  resins  are  mixtures  of  hard  resins,  oils, 
and  gums.     Among  these  are  aloes,  asafoetida,  galbanum, 
guaiacum,  myrrh,  etc.     Burgundy  pitch  and  Mecca  bal- 
sam are  oleo-resins. 


TERPENES  AND  RESINS.  423 

Caoutchouc,  or  India  rubber,  is  found  in  the  juices  of 
many  plants  growing  in  the  tropics.  It  is  a  mixture 
of  several  isomeric  terpenes.  When  pure,  it  is  a  soft, 
white  mass,  characterized  by  great  elasticity.  It  is  solu- 
ble in  naphtha  and  carbon  bisulphide,  and  is  left  un- 
changed when  these  solvents  evaporate.  It  combines 
with  sulphur  to  form  what  js  known  as  vulcanized 
rubber. 

The  ordinary  vulcanized  rubber  is  produced  By  heating  caout- 
chouc with  a  small  quantity  of  sulphur  (5-10%)  to  about  140°, 
The  vulcanized  rubber  differs  in  many  respects  from  the  natural 
caoutchouc,  being  less  readily  soluble,  and  better  able  to  resist  the 
action  of  the  atmosphere  and  of  chemical  re-agents.  It  is  used 
extensively  in  rubber  tubing,  over-shoes,  etc.  Ebonite  is  the  hard 
rubber  used  in  knife  handles,  buttons,  etc.,  and  contains  a  larger 
amount  of  sulphur,  carefully  incorporated  by  heating  and  pressure. 

Gutta-percha  is  the  thickened  juice  of  the  Isonandra 
gutta.  It  is  a  tough,  inelastic  substance,  similar  in  many 
respects  to  caoutchouc.  When  heated  in  boiling  water, 
it  softens,  and  becomes  so  pliable  that  it  can  be  made 
to  assume  any  form,  and  retains  this  on  cooling.  It  is 
extensively  used  for  insulating  telegraph  wires. 


Recapitulation. 

(1)  The  aromatic  hydrocarbons  are  regarded  as  formed  upon  the 
benzene  nucleus,  C6H6. 

(2)  Two  benzene  groups  may  unite,  as  in  di-phenyl,  C6H5  •  C6H5, 
and  so  uniting  suffer  condensation. 

(3)  The   benzene   nucleus,  whether   simple   or  condensed,    may   be 
modified    by  'changes  within    the   nucleus,  or   by  additions   of 
"  lateral  chains,"  and  so  give  rise  to  two  classes  of  isomers. 

(4)  The  di-derivatives   form  ortho,  meta,  and   para  compounds, — 
o,  m,  p.     The   tri-derivatives   form   consecutive,  1,  2,  3;   sym- 
metricalt  lt  3,  5;  and  unsymmetrical  compounds,  1,  2,  4. 


424  ORGANIC  CHEMISTRY. 

(5)  Many  of   these  are  obtainable   from   coal-tar,  as   benzene,  an- 
thracene.    The   terpenes    are   natural    hydrocarbons,  related   to 
cymene.     Many  essential  oils  are  isomers  of  terpene. 

The  camphors  are  oxidized  terpenes. 

(6)  Many  of   the  hydrocarbons  are  useful    in  the  arts,  as   turpen- 
tine, the   resins,  and   balsams.     The   others   are   important  by 
reason  of  their  derivatives,  notably  the  "coal-tar  colors." 


a 

19 


«  3                £  * 

— -     —  - 

1. 

r  ^ 


O  0  ? 

i-          I  s 

*          i  & 

B 

I  S 


s:  o  r  t  H     a 

»  3=  S  I  s    B 
s  2   r  !  i     o 


CHAPTER   XXYIT. 

AROMATIC    COMPOUNDS    CONTAINING    O    AND    OH. 

782.  The  aromatic  hydrocarbons  form  two  classes  of 
hydroxyl  derivatives,  which  are  metameric  with  each 
other.  (1)  The  phenols,  formed  by  substituting  in  C6H6 
the  benzene  nucleus,  OH  for  H,  as  phenol,  C6H5OH  ;  cate- 
chol,  C6H4(OH)2;  and  pyrogallol,  C6H3(OH)3.  (2)  The 
aromatic  alcohols,  formed  by  the  same  substitution  in  the 
lateral  chain;  as,  benzyl  alcohol,  C6H5CH2OH. 

PARTIAL  LIST  OF  PHENOLS. 

Monohydric. 

C6  H6  O,  Phenol,       ....  C6H5  •  OH. 

C7  H8  O,  Cresols.(o.m.p.),     .         .  C6H4(CH3)  OH. 

C8  H100,  Xylenols,    ....  C6H3(CH3)2OH. 

Ethyl  phenols  (phlorol),  C6H4(C2H5)  OH. 

C9  H12O,  Messitols,         .        .        .  C6H2(CH3)3OH. 

Propyl  phenols,          ..       .  C6H4(C3H7)  OH. 

C10H140,  Thymols,    1,  3,  4,  .  C6H3(CH3)(C3H7)OH. 

Carvacrols,   1,  2,  4  and  carvols. 

Di-hydric. 

C6H6  O2,  Pyrocatechin,    resorcin,   hydroquinone,   C6H4(OH)2. 
C7H8  O2,  Orcin,  homo-pyrocatechin,    .         C6H3  CH3(OH)2. 
C8H10O2,  /3,  orcin,  hydrophlorone,  .     C6H2(CII3)2(OH)2. 

Tri-hydric. 
C6H6  03,  Pyrogallol,  phloroglucin,     .         .     C6H3(OH)3. 


426  ORGANIC  CHEMISTRY. 

783.  The  phenols  resemble  the  tertiary  alcohols  in  most 
of  their  chemical   properties,  but  were  formerly  regarded 
as  acids  because  they  form  salts,  like  C6H5ONa,  by  the 
action    of   the    basic    hydroxides.     They   may  be    formed 
from  the  benzene  hydrocarbons  (\)  by  fusing  their  sul- 
phonic   salts  with   caustic   potash,  C6ir5SO2OK,  benzene 
sulphonate  -f  KOIl  -- =  K2$O4  -f  r6TT5O3I  =--  phenol,  or 
(2),  by  the  action  of  nitrous  acid   upon   the  amines;   as, 
C6II5Xir2-aniline-|-XOOir-X2-i  H20  +  C61I5OII. 

The  principal  source  of  the  lower  members  is  the  heavy  oil  of 
tar  already  mentioned.  To  prepare  them  (1)  the  crude  oil  is 
shaken  up  with  the  aqueous  solution  of  an  alkali  (soda).  In  the 
course  of  time,  an  alkaline  phenate,  etc.,  forms  and  dissolves  in  the 
water.  This  solution  is  drawn  oil'  and  decomposed  by  hydrochloric 
acid.  Tlu«  oily  product  thus  formed  is  separated  hy  fractional  dis- 
tillation. The  portion  which  distills  between  180°-200°C  is  mostly 
phenol. 

784.  Phenol,  rfiII-OII,  which  gives  the  generic  name 
to  this  class  of  compounds,  is  usually  termed  carbolic  acid. 
When  pure,  it  crystallizes  in  colorless  prisms,  which  melt 
at  40°(1  (boil  at  lS:i°C;  sp.  gr.,  1.08),  and  dissolve  in   15 
parts  of  water.     Phenol  lias  a  smoky  odor,  a  sharp,  burn- 
ing  taste,   and    is   a    powerful   escharotic.     It  coagulates 
albumin,  and   consequently  acts  as  an  energetic  poison. 
It  is  an  excellent  disinfectant  and  antiseptic,  and  is  used 
also  in  the  manufacture  of  the  aniline  colors.     Its  aque- 
ous  solution,  dropped    upon   a    pine   shaving   previously 
moistened  by  JIC1,  produces  a  permanent  blue  stain  ;  (2) 
added  to  ferric  chloride  solution,  yields  a  beautiful  violet; 
(3)   to  bromine   water,   even  when   very  dilute,  a  white 
precipitate  of  tri-brom  phenol,  C6TT2Br3OII. 

The  phenols,  when  added  to  alkaline  solutions,  form 
white  crystalline  salts  ;  as,  C6H5ONa,  sodium  phenate. 
Such  salts,  when  heated  with  alkyl  iodides,  yield  com- 
pounds which  resemble  the  mixed  ethers.  For  example, 
C6H5ONa  -f  CH3I  =  Nal  +  C6H-  •  O  •  CH3  =  anisol,  a 


PHENOLS.  427 

colorless,   fragrant   liquid,  which    may   also   be   obtained 
from  the  volatile  oil  of  anise. 

785.  The  phenols  and  their  cogeners  easily  form  sub- 
stitution products,  by  exchange  of  hydrogen  in  the  ben- 
zene   nucleus    for   Cl,  or    NO2,  and   the   like.     Many  of 
these   products  have   strongly  acid   properties.     For   ex- 
ample, by  the   action  of  nitric  acid    upon    phenol,  there 
are  formed  (1)  three  mono-nitro  phenols,  C6II4NO2OH; 
(2)  five  di-nitro  phenols,  C6H3(]SrO2)2OII;   (3)   two  tri- 
nitro   phenols,  C6II2(NO2)3O1I;    and   many  others   are 
possible.     The  most  important  is 

Picric  acid,  C6II2(NO2)3OH  (1:2:4:6),  also  called 
carbazotic  acid.  It  may  also  be  obtained  from  other  or- 
ganic bodies, — as  indigo,  silk,  wrool,  etc., — by  the  action 
of  strong  nitric  acid.  Picric  acid  is  sparingly  soluble  in 
H2O,  but  readily  in  C2I15OII,  and  crystallizes  out  from 
hot  alcohol  in  beautiful  pale-yellow  plates,  which  melt  at 
122°.  and  explode  when  heated  strongly.  Its  alcoholic 
solution  has  an  intensely  bitter  taste,  and  is  used  as  a 
substitute  for  hops  in  beer,  and  as  an  excellent  yellow 
dye  for  silk  and  wool. 

Potassium  picrate,  C6H2(NO2)3OK,  is  a  yellow  salt,  which  ex- 
plodes violently  both  by  heating  and  by  percussion.  It  is  used  in 
fire- works. 

786.  The    substances    sold   as    creasote   are    mixtures. 
That  obtained  from  coal-tar  is  principally  phenol ;   that 
from  beech-tar  is  mainly  cresol,  but  both  contain  guaia- 
col,  and  other  such  bodies.     The  odor  observed  in  smoked 
ham  and  in  Scotch  whiskey  is  due  to  some  sort  of  crea- 
sote.    Creasote   is   used,  as   its   name  implies,  as   a  flesh 
preserver,  and  is  considered  a  valuable  antiseptic. 

The  three  cresols,  C6H4CH3OH  (ortho,  para,  meta), 
are  not  easily  separated.  They  may  be  obtained  pure 
from  the  sulphonic  acids  of  toluene,  C6H4CH3SO2OH. 

They  are  isomeric  with  benzyl  alcohol,  C6H5CH2OH, 


428  ORGANIC  CHEMISTRY. 

but,  nevertheless,  resemble  their  homologue,  phenol,  in 
most  of  their  properties  and  reactions. 

Three  ten-carbon  phenols,  C,0H13OH,  are  known.  Thymol  is  pro- 
pyl-meta-cresol,  found  in  the  oils  of  thyme  and  horse-mint.  Car- 
vacrol  is  propyl-ortho-cresol,  found  in  the  oil  of  origanum,  hut  hest 
obtained  from  its  isomer,  carvol,  which  is  an  alcohol  existing  in 
the  oil  of  caraway. 

787.  The   di-hydric   phenols   resemble  the   phenols  in 
most  of  their  chemical  reactions,  except  that  they  have 
two  hydroxyl  radicals  for  exchange.     Ferric  chloride  pro- 
duces, in   the  ortho  and   meta  compounds,  characteristic 
colors  (green  to  violet),  but  oxidizes  the  para  di-hydric 
phenols   to  quinones.     They  may  be  obtained  by  fusing 
the    sulphonic    acids,    or    the    haloid    derivatives   of  the 
phenols  with  caustic  potash, 

C6II4BrOII  +  KOH  =  KBr-f  C6H4(OH)2. 

All  may  bo  volatilized  without  decomposition,  and  most 
of  them  may  be  found  among  the  products  of  the  dry 
distillation  of  the  aromatic  acids,  resins,  etc.,  and  also  of 
cellulose. 

788.  Catechol,  or  pyrocatechin,  (o.),  C6H4(OII)2,  is  a 
solid  below  104°;  boils  at  245°,  and  readily  sublimes  to 
shining   plates.     It  is  most  readily  prepared   by  heating 
its  methyl  ether,  guaiacol,  with   hydriodic  acid.     Guaia- 
col,  C6H3  •  O  •  C6II4  •  OH,  is  a  fragrant,  colorless  liquid, 
boiling  at  200°,  obtained  from  guaiacum  resin. 

Resorcinol,  (m.),  C6H4(OH)2,  is  obtained  by  dry  dis- 
tillation of  Brazil  wood  extract.  Its  most  characteristic 
reaction  is  obtained  by  heating  it  for  a  few  minutes  with 
phthalic  anhydride,  C6H4(COOH)2,  whereby  fluorescein 
is  produced,  which  dissolves  in  dilute  alkalies  with  a 
splendid  green  fluorescence. 

Hydroquinone,  or  quinol,  (p.),  C6H4(OH)2,  is  easiest 
made  by  the  reduction  of  quinone  with  sulphurous  acid. 
Oxidizing  agents  reconvert  hydroquinone  to  quinone.  In 


QUINONES.  429 

both  these  operations,  an  intermediate  compound,  quin- 
hydrone  is  produced,  which  gives  a  brown  color  to  the 
solution.  Quinone  is  usually  made  by  oxidizing  aniline, 
C6H5NH2,  with  chromic  mixture. 

HO    C6H4  OH.      HO-C6H4         C6H4-  OH.  O 

C6H4<  | 

O-         -O  O 

Hydroquinone.  Quinhydrone.  Quinone. 

Hydroquinone  crystallizes  from  an  aqueous  solution  in 
hexagonal  prisms,  which  have  a  sweetish  taste,  and  which 
melt  at  169°.  Quinhydrone  crystallizes  in  splendid  gold- 
green  prisms,  which  form  green  solutions  with  alcohol, 
and  brown  solutions  with  hot  water. 

Quinone,  C6H4O2,  forms  golden-yellow  needles,  more 
easily  soluble  in  hot  water  than  in  cold,  which  melt  at 
11G°,  and  volatilize  even  at  ordinary  temperatures.  The 
vapor  has  an  odor  which  resembles  that  of  iodine,  and 
is  exceedingly  irritating  to  the  eyes. 

QUINONE  must  be  taken  by  the  student  to  represent  an  entire 
class  of  aromatic  compounds,  produced  by  the  oxidation  of  the 
para  derivatives  of  the  benzene  hydrocarbons.  In  these  compounds 
two  hydrogen  atoms  (1  : 4)  are  replaced  by  two  oxygen  atoms, 
united  directly  to  two  carbon  atoms,  either  as  a  dyad  group,  or 
after  the  manner  of  a  double  ketone;  thus, 


HC 


By  partial  reduction  of  these  bodies  quinhydrones  are  produced; 
by  complete  reduction,  the  para-hydroxy-phenols. 


430  ORGANIC  CHEMISTRY. 

The  quinones  are  usually  solids  of  a  yellow  color,  easily  dis- 
tilled by  the  aid  of  steam,  and  readily  forming  substitution  prod- 
ucts with  Cl,  etc. 

789.  Orcin,  or  orcinol,  C6II3CII3(OII)2,  is  found  in  all 
those  lichens  from  which  archil,  cudbear,  and  litmus  are 
prepared,  and  results  from  the  decomposition  of  the  acids 
extracted  from  them,  —  orsellinic,  erythric,  etc.     It  crys- 
tallizes  in    colorless   six-sided    prisms,   freely  soluble   in 
water,  and  of  a  sweetish  taste. 

790.  Of  the  tri-hydric   phenols,  the  most  important  is 
pyrogallol,   or    pyrogallic   acid,   C6II3(()II)3.     It    is   pre- 
pared by  heating  gallic  acid   in  a  stream  of  carbonic  an- 
hydride, and   crystallizes  in    thin  colorless   plates,  which 
melt  at  115°;  sp.  gr.,  1.45.     It  has  a  bitter  taste,  and  is 
an    active   poison.     When    dissolved    in    the   solutions  of 
the  alkalies,  it  rapidly  absorbs  oxygen  from  the  air,  and 
becomes  converted  to  acetic  and  carbonic  acids  and  cer- 
tain brown,  humus-like  bodies  (Exp.  78).     It  also  reduces 
the  salts  of  gold  and  silver,  and  for  this  reason  is  some- 
times used  in  photography.     Pure  ferrous  salts  give,  with 
pure   pyrogallol,   only   a    white    cloudiness,   but   if  ferric 
salts   are   likewise   present,  the   color  becomes  first  blue 
and  finally  red. 

Phloroylucol,  C6H3(OII)3,  may  be  prepared  by  fusing  potassium 
hydroxide  with  gamboge,  dragon's  blood,  and  similar  substances, 
and  from  glucosides,  like  the  phloridzin  which  is  found  in  the 
root-bark  of  many  fruit-trees.  When  chlorine  is  passed  into  its 
aqueous  solution,  phloroglucol  is  converted  to  di-chlor  acetic  acid, 
C6H603+  3H20  +  C112=6HC1  +  3(C2C12H202). 


791.  Besides  the  phenol  dyes  occuring  naturally,  like 
litmus,  may  be  mentioned  a  few  artificially  prepared. 

Aurine,  or  coralline,  is  a  fine  scarlet-red  dye,  produced  by  heat- 
ing a  mixture  of  phenol  and  sulphuric  acid,  and  then  gradually 
adding  oxalic  acid  until  CO2  ceases  to  be  evolved;  as, 

3(C6H5OH)+(COOH)3=CH202,  formic   acid-f  C19H14O3=atirine. 


PHENOL  DYES.-  431 

The  reaction  is  in  reality  more  complex,  and  the  product  a  mix- 
ture, from  which  pure  aurine,  C19H14O3,  may  be  obtained  as  ruby- 
red  crystals  of  a  tine  green  lustre. 

Rosolic  acid,  C20H16O3,  is  the  homologue  of  the  preceding,  and 
is  made  from  rosaniline  by  the  action  of  nitrous  acid.  It  closely 
resembles  aurine  in  appearance  and  properties.  When  heated  above 
270°  it  yields  phenol,  and  hence  may  be  regarded  as  intermediate 
between  the  hypothetical  phthale'in  and  rosaniline  (§  824). 

C6H5  C6H5  OHC6H4  C6H3CH3 


C6H5  H  OHC6H4  0 

Phthale'in.  Kosolic  acid. 

NH2-C6H4 

NH2    0^4  NH2. 

Kosaniline. 

The  phthale'ins  are  prepared  by  heating  the  mixture  of  a  phenol 
and  phthalic  anhydride,  C6H4:C2O3,  with  strong  sulphuric  acid. 
The  phthale'ins  are  soluble  in  alkaline  liquids  with  fine  and  char- 
acteristic colors.  Such  solutions,  when  boiled  with  zinc,  add  H2, 
and  are  reduced  to  phthalins,  which  are  colorless  bodies,  easily  re- 
converted to  the  phthale'ins  by  oxidation,  and  which  dissolve  in 
strong  H2SO4,  losing  H2O,  and  becoming  phthalidins.  Among  these 
products  are  : 

Phenol  phthalein,  C6H4(CO  •  C6H4  •  OH)2,  a  yellowish  white 
powder,  soluble  in  dilute  alkalies,  with  fine  red  color.  This  color 
disappears  when  the  acid  is  neutralized.  It  is  sometimes  employed 
as  an  indicator  in  volumetric  analysis. 

Fluorescein  is  resorcin  phthalein,  C6H4(CO  •  C6H3  •  OH)2O,  which 
is  precipitated  from  its  solutions  in  alkalies  by  H2SO4  in  yellowish 
flocks,  which  become  of  a  yellowish-red  when  dried.  The  solution 
in  dilute  alkalies  exhibits  a  splendid  green  fluorescence.  It  is  con- 
verted by  bromine  to  eorin,  C6H4(CO  •  C6HBr2  •  OH)2O,  which  is 
sold  as  a  brick-red  powder,  dissolving  in  alcohol  to  a  reddish-yellow 
solution.  The  trace  of  an  alkali  produces  in  this  a  splendid  golden- 
green  fluorescence.  The  potassium  salt,  C6H4(CO  •  C6HBr2-  OK)2O, 
is  used  for  dyeing  silk  a  rose-red  color. 

792.  The  aromatic  alcohols  are  mostly  primary,  con- 
taining the  group  CH2OH  attached  to  the  benzene 
nucleus  in  a  lateral  chain.  The  most  of  them  are  pre- 


432  ORGANIC  CHEMISTRY. 

pared  from  the  corresponding  chlorides  of  the  hydrocar- 
bons, or  from  the  natural  resins  and  volatile  oils.  They 
agree  in  most  of  their  chemical  properties  with  the  al- 
cohols of  the  fatty  series  (1)  as  to  the  methods  by  which 
they  are  obtained;  (2)  as  to  the  products  which  they 
may  be  made  to  yield,  the  reactions  being  in  both  duo 
to  changes  which  take  place  in  the  radicals,  Cli2OH 
and  CHOH. 

793.  Benzyl  alcohol,  C6H5  CII2OII,  occurs  in  Peru 
and  tolu  balsams,  principally  as  benzyl  bcnzoate  and 
cinnamate.  It  may  be  prepared  from  either  of  these  by 
saponification, 


C6H6CH2  •  O  •  C  JI  5CO  =  benzyl  benzonte+ 

C6H6COOK  =  potassium  benzoate  +  C6H5  •  CH2OH. 

Also,  by  the  reduction  of  its  aldehyde,  the  oil  of  bitter 
almonds,  or  of  benzole  acid.  It  is  a  colorless  liquid, 
having  a  faint  aromatic  odor;  sp.  gr  ,  1.063;  boiling  at 
206.5°;  insoluble  in  water,  but  freely  soluble  in  ethyl 
alcohol.  Weak  oxidizing  agents  convert  it  into  benzoio 
aldehyde,  and  stronger  into  benzole  acid. 

Benzyl  alcohol  is  converted  by  the  action  of  strong  HC1  into 
benzyl  chloride,  C6H5CH2C1,  a  colorless  liquid,  with  pungent  vapor, 
which  boils  at  176°.  This  compound  is  also  formed  when  chlorine 
is  passed  into  boiling  toluene,  C6H5CH3+C12:=HC1+C6H5CH2CL 
Benzyl  chloride  is  used  in  the  preparation  of  most  benzyl  com- 
pounds. (1)  Giving,  with  KHS,  benzyl  mercaptan,  C6H5CH2SH, 
and  other  sulphides;  (2)  with  NH3,  benzyl  amine,  C6H5CH2NH2, 
a  substance  from  which  the  mustard-oils,  etc.,  have  been  prepared; 
(3)  when  boiled  with  the  potassium  salts  of  the  organic  acids,  form- 
ing the  ethereal  salts  of  benzyl;  as,  benzyl  acetate, 

C6H5CH2C1  +  KC2H3O2  =  KC1  +  C6H5CH2     O    C2H3O. 

794.  About  a  dozen  higher  homologues  have  been  de- 
scribed. Among  them  are  the  secondary  phenyl-ethyl  al- 


THE  AROMATIC  ALCOHOLS.  433 

cohol,  C6H5  •  CHOH  •  CH3,  which  oxidizes  to  the  ketone, 
C6H5  •  CO  •  CH3,  aceto-phenone.  and  benzhydrol, 

C6H5  -CHOH-C.H., 

which   oxidizes   to   benzophenone,  C6H5   CO  •  C6H5,  and 
triphenyl  carbinol,  (C6H5)8COH. 

795.  Cumyl  alcohol,  C10H14O,  which,  together  with  cy- 
mene,  occurs  in  Horn  an  caraway  oil,  bears  the  same  rela- 
tion to  the  ten  carbon  phenols  and  cymene  that  benzyl 
alcohol  does  to  the  cresols  and  toluene. 

Cinnyl  alcohol,  C6H5  CH  :  CH  CH2OH,  is  supposed 
to  contain  the  monovalent  allyl,  (CH0  :  CH  •  CH2)'. 
It  may  be  obtained  by  distilling  a  mixture  of  storax 
with  caustic  potash,  in  silky  needles,  which  have  the 
pleasant  odor  of  hyacinths,  and  which  melt  at  33°C  to 
an  oily  liquid.  Upon  oxidation,  it  is  converted  to  cin- 
namic  aldehyde,  and  then  to  cinnamic  acid.  It  is,  there 
fore,  related  to  these  substances  in  the  same  way  that 
allyl  alcohol  is  related  to  acrolein  and  to  acrylic  acid. 

796.  Cholesterin,    C25H41CH2OH,   occurs    in    various 
parts  of  the  animal  system,  but  especially  in  the  brain 
and  the  bile.     The  biliary  calculi  are  frequently  almost 
pure  cholesterin.     It  may  be  obtained  by  dissolving  these 
in  a  mixture  of  alcohol   and  ether.     Upon   crystallizing, 
it  forms  in  white  plates  of  a  fatty  feel,  and  a  mother-of- 
pearl  lustre,  melting  at  145°  ;  sp.  gr.,  1.06.     It  is  soluble 
in  chloroform.     The  chloroform  solution,  shaken  with  an 
equal  volume  of  strong  sulphuric  acid,  becomes  at  first 
blood-red,  and  finally  purple,  while  the  acid  takes  on  a 
greenish  fluorescence.     If  the  chloroform  solution  be  then 
decanted  and  allowed  to  evaporate,  it  becomes  blue,  then 
green,  and  at  last  yellow.     These  reactions   serve  as   a 
test  for  cholesterin. 

797.  The   phenol   alcohols   contain    two  or  more    hy- 
droxyl  groups,  one   of  which   is   directly  united  to  the 

Cbem.— 28, 


434  ORGANIC  CHEMISTRY. 

nucleus,  and  one  in  the  lateral  chain.  They  are  pre- 
pared by  reducing  their  aldehydes  with  sodium  amalgam. 
Saligenin,  HO  •  C6H4  •  riI2OH,  is  ort ho -oxy benzyl 
alcohol,  best  made  from  salicin  (a  glucoside  found  in 
willow  bark) 'by  the  action  of  the  ferment,  emulsin;  thus, 
C18H18O7,  salicin  -f  H2O  =  C6II12O6  +  (17H8O2,  sal- 
igenin.  After  the  mixture  has  been  digested  for  a  day, 
the  alcohol  is  extracted  by  shaking  with  ether,  and  puri- 
fied by  recry stall iz ing.  It  forms  rhombic  tables  which 
melt  at  82°,  and  sublime  below  100°;  sp.  gr.,  1.16.  It  is 
soluble  in  water,  and  is  easily  converted  by  oxidizing 
agents  into  salicylic  aldehyde  and  salicylic  acid. 

798.  Very  interesting  are  a  number  of  substances  of 
this  group,  which  contain  methyl  oxide  in  place  of  the 
phenol  hydroxyl,  in  the  same  sense  of  the  words  that 
anisyl  alcohol,  CH8O  •  C6H4  •  CII2OH,  may  be  regarded 
as  the  methyl  ether  of  saligenin,  and  which  may  easily 
be  prepared  b}*  boiling  anisic  aldehyde  with  an  alcoholic 
solution  of  potash. 

VanilUc  alcohol,  CH3O,  OH,  C6H,  •  CH2OII,  is  obtained 
by  the  oxidation  of  the  vanillin  in  vanilla  beans,  and 
also  from  coniferin.  Coniferin,  016H22O8,  is  a  crystal- 
line glucoside  found  in  the  cambium  larger  of  pine  trees. 
It  forms,  on  fermentation, 

coniferyl  alcohol,  CH3O,  OH,  C6H3  •  CH  :  CII  •  CH2OH. 

Eugenol,  CH3O,  OH,  C6H3  •  CH:  CH  CH3,  occurs  in 
the  oils  of  cloves  and  of  pimento.  The  two  latter  con- 
tain the  radical  allyl,  and  are  closely  related  to  ferulic 
acid,  (OH) 2  :  C6H3  •  C3H4COOH,  which  is  found  in 
asafoedita.  All  of  these  compounds  may  be  made  to 
yield  protocatechuic  acid,  C6H3(OH)2COOH. 

A  few  phenols  have  been  described  which  contain 
two  or  three  benzene  nuclei.  Among  these  are  di-phenol, 
HO  •  C6H4-  C6H4-  OH;  »  and  ft  naphthols,  C10H7OH; 


THE  AROMATIC  ALDEHYDES.  435 

and    the    metamers,    anthranol    and    anthrol,    C14H9OH. 
Also,  oxidation  products,  like  — 

naphthoquinone,  C10H6<Q>, 

which,    on    further    oxidation,    is    converted    to    (ortho) 
phthalic   acid,   C6H4(COOH)2,  and  the  very  important 

anthraquinone,  C6H4<^>C6H4.  §774. 

THE  ALDEHYDES. 

799.  The  aldehydes  of  these  alcohols  are  constituents 
of  many  of  the  oils  found  in  the  spices  and  flavors. 

Benzaldehyde  is  the  oil  of  bitter  almonds,  C6H5-CHO. 
It  is  prepared  from  amygdalin  by  the  fermentation  in- 
duced by  emulsin.  These  substances  are  found  in  the  milk 
of  almonds  and  similar  stone-fruits,  and  the  decomposition 
takes  place  when  the  crushed  almonds  are  digested  for 
for  some  hours  with  luke-warm  water,  C20H27NO11, 
amygdalin  +  2H2O  =  2CQKl 2O6  +  HCN  +  C6H5  •  CHO. 

Glucose  and  prussic  acid  are  produced  at  the  same  time.  It  is 
freed  from  these  by  shaking  the  crude  product  with  Fe2CI6  and 
Ca(OH)2,  and  distilling.  It  may  also  be  prepared  from  numerous 
other  substances;  as,  toluol,  C6H5CH3,  benzoic  acid,  and  the  al- 
bumins. 

Pure  benzaldehyde  is  a  colorless  liquid,  of  a  peculiar 
aromatic  odor,  and  is  not  poisonous;  sp.  gr.,  1.063;  boils 
at  179°.  It  is  readily  soluble  in  alcohol,  very  sparingly 
in  water,  and  is  used  for  flavoring  confectionery.  It 
oxidizes,  when  exposed  to  the  air,  to  benzoic  acid;  is 
reduced  by  sodium  amalgam  to  benzyl  alcohol. 

All  the  aromatic  aldehydes,  like  those  of  the  fatty  series,  form 
beautiful  crystalline  compounds  with  the  alkaline  bi-sulphites,  but 
they  behave  differently  with  ammonia,  forming  neutral  bodies 
known  as  hydramides.  Hydro-benzamide  is  formed  by  the  reaction, 
3C6H5  •  CHO  +  2NH3  =  3HaO  +  (C6H5CH)3N2.  When  heated  to 


436  ORGANIC  CHEMISTRY. 

130°  it  becomes  the  strongly  basic  etmarin*,  C21H18Na,  which  is  its 

isomer.  The  latter  is  jxjisonoiis;  the  former  is  not.  Both  are 
readily  soluble  in  alcohol. 

800.  Cumic  aldehyde,  r,.II4  C3II7,  CIK),  is  found  in 
the  oils  of  cumin   and  water  hemlock,  together  with  cy- 
mene.     It  may  be  obtained   from  these   by  first   forming 
its  compound  with  acid  sodium  sulphite,  and  then  distill- 
ing this  product  with  caustic  soda.     It  is  a  liquid  having 
the  odor  of  caraway  seeds;    sp.  gr.,  0.!>S;    l,0ils  at  237°; 
and    is   converted    by   alcoholic   potash    to   cumyl   alcohol 
and   potassium   cumate. 

801.  Cinnamic  aldehyde,  C'fiII  -  TIT  :  TIT    TITO,  is  the 
chief  constituent  of  the  oils  of  cinnamon  and  cassia.     It 
may  be   made  synthetically  by  saturating  a  mixture  of 
benzaldchyde  and  acetic  aldehyde  with  IICl.  and  heating 

c6H5ciio  +  oiijCiio  =  ii 26  f  cr, ir,  rn  :  en  •  OHO 

(see  §668").  It  is  a  colorless  liquid,  heavier  than  water, 
and  oxidizing,  on  exposure  to  the  air,  to  cinnamic  acid, 
and  then  to  benzaldehyde. 

802.  Salicylic  aldehyde  (o.),  OH    Cr>H4    CIIO,  occurs 
in  the  flowers  of  the  spiraeas.     It  may  be  prepared  from 
saligcnin    by   oxidizing   with   chromic   mixture,  or   more 
easily  by  heating  a   mixture  of  chloroform,  sodium   hy- 
droxide, and  phenol : 

(a)  CHCl3+3NaHO:=H20  +  HCOOII^  formic  acid. 
(6)  HCOOH  +  C6II5OII  = 

II2O  -f  HO  •  C6II4  •  CHO  =  salicylic  aldehyde. 

At  the  same  time  its  isomer,  para  oxybenzoic  aldehyde, 
is  formed;  the  two  are  separated  by  distillation,  the  sal- 
icylic aldehyde  passing  over  as  an  aromatic  oil,  slightly 
soluble  in  water,  and  boiling  at  196°;  sp.  gr.,  1.17.  As 
it  contains  the  phenol  hydroxyl,  it  has  weak  acid  prop- 
erties, and  is  sometimes,  but  improperly,  termed  salicyl- 
ous  acid. 


THE  AROMATIC  ACIDS.  437 

The  oils  of  anise,  fennel,  etc.,  contain  anethol,  CH3O  •  C6H4  •  C3H5, 
which  is  probably  the  methyl  ether  of  allyl  phenol.  On  warming 
these  oils  with  dilute  nitric  acid,  anisic  aldehyde  is  produced, 
CH3O  •  C6H4  •  CHO.  This  is  a  fragrant  liquid;  sp.  gr.,  1.12;  boil- 
ing at  250°;  and  is  readily  converted  to  anisyl  alcohol,  and  to 
anisic  acid. 

About  two  per  rent  of  vanillin,  CH3O  Cr,IT3  •  OH,  CHO,  is 
found  in  vanilla  beans,  often  in  crystals.  It  may  be  obtained  ar- 
tificially from  coniferin  by  oxidation  with  chromic  acid  mixture. 
It  is  the  methyl  ether  of  the  aldehyde  of  protocatechuic  acid. 
Vanillin  crystallizes  in  groups  of  colorless  needles,  which  melt  at 
80°,  and  sublime  at  150°.  The  well  known  vanilla  flavoring  extract 
is  made  from  it. 

THE  AROMATIC  ACIDS. 

803.  Many  of  the  aromatic  acids  occur  among  the 
natural  products  of  plants  and  animals;  others  are  pre- 
pared from  the  aromatic  hydrocarbons  by  oxidation  with 
chromic  mixture.  So,  also,  like  the  acids  of  the  fatty 
series,  they  may  be  obtained  by  oxidizing  their  alde- 
hydes and  alcohols,  and  they  may  be  reduced  to  these 
compounds  by  nascent  hydrogen.  They  differ  from  the 
fatty  acids  in  some  particulars,  being  all  of  them  solids, 
having  comparatively  high  melting  and  boiling  points, 
slightly  soluble  in  water,  but  easily  in  alcohol  and  ether. 
All  of  them  may  be  distilled  by  the  aid  of  steam,  and 
some  may  be  sublimed  in  the  dry  state  without  decom- 
position. The  sodium  salts  of  these  acids  may  be  pre- 
pared synthetically  by  the  joint  action  of  sodium  and 
carbonic  anhydride  upon  their  mono-brom  derivatives; 
as,  e.  </.,  sodium  benzoate;  thus, 

C6H5Br  +  Na2  +  CO2  =  NaBr  +  C6H5  •  COONa, 

and  the  acid  obtained   free  by  subsequent  treatment  of 
the  product  with  strong  hydrochloric  acid. 

The  calcium  salts  of  the  aromatic  acids,  (1)  heated  by 
themselves,  produce  ketones;  e.  g., 


438 


ORGANIC  CHEMISTRY. 


(2)  heated  with  calcium  formate,  they  produce  the  cor- 
responding aldehyde;  as, 

(C6H6COO)2Ca  -f  (HCOO)2Ca  - 

2CaCO3  +  2(C6II5CHO)  =  benzaldehyde, 

which  may  be  reduced  to  the  primary  alcohol ;  as,  benzyl 
alcohol,  C6II5CII2OH.  The  acids,  heated  with  quicklime, 
exchange  the  COOII  group  for  II,  and  evolve  a  hydrocar- 
bon;  as,  C6II5COOH  -f-  CaO^rCaCO3  -  CCIIG  ^benzene. 

804.  Benzole  acid,  C6II5COOII,  is  a  constituent  of 
various  gums  and  balsams,  and  is  one  of  the  products  of 
the  oxidation  of  a  great  variety  of  organic  substances. 
Its  chief  source  is  hijtpuric  acid,  which  is  found  in  the 
urine  of  herbivorous  animals,  and  which  is  decomposed 
on  boiling  with  acids  into  glycocine  and  benzole  acid, 
C6II5  •  CO  •  Nil  CII2  •  COOII  +  II20  ==  CH2  •  NII2, 

COOII  -f  C6II5COOII.  It 
is  best  prepared  by  heating 
gumbenzoin  in  an  iron  pan, 
loosely  covered  by  a  hood 
of  filter  paper.  The  acid 
begins  to  sublime  at  about 
100°,  and  collects  upon  the 
paper  in  shining,  feathery 
crystals,  which  melt  at  121° 
and  boil  at  240°.  Its  va- 
pors, when  dilute,  have  a 
pleasant  aromatic  odor,  but 
when  freely  evolved  pro- 
duce coughing. 

The  salts  of  benzoic  acid  re- 
semble the  acetates.  The  alka- 
line benzoates  are  freely  soluble 
in  water,  and  produce,  when  added  to  hot  neutral  solutions  of 
ferric  salts,  a  red-brown  amorphous  precipitate  of  basic  ferric 
benzoate,  which  is  quite  insoluble  in  water. 


<;.  108. 


THE  AROMATIC  ACIDS.  439 

The  ethers  are  of  much  higher  boiling  point  than  those  of  acetic 
acid,  ethylic  benzoate,  C2H5  •  O  •  C7H5O,  boiling  at  211°. 

The  liquid  portion  of  Peru  balsam  is  chiefly  benzylic  benzoate, 
C6H5CH2  •  O  •  C6H5CO,  which  boils  at  345°.  " 

805.  A  very  large  number  of  derivatives  have  been 
obtained  from  benzole  acid.  For  example,  when  it  is 
distilled  with  PC15,  it  yields  C6II5COC1,  benzoyl  chloride, 
a  pungent-smelling,  colorless  liquid,  boiling  at  199°,  and 
exceedingly  active  in  metathetical  reactions,  forming  (1) 
with  KBr,  KCN,  etc.,  benzoyl  bromides,  cyanides,  etc.; 
(2)  with  sodium  salts  of  the  organic  acids,  a  variety  of 
anhydrides;  as,  benzoic  anhydride,  (C7H5O)2O;  aceto-ben- 
zoic  anhydride,  C2II3O  •  O  •  C7H5O;  (3)  with  ammonia, 
benzamide,  C6H5CONII2,  a  weak  base  soluble  in  hot 
water;  and,  finally,  benzo-nitril,  C7H5N;  (4)  with  silver 
glycocine,  benzoyl  glycocine,  which  is  hippuric  acid, 


CH2  •  NAgH  •  COOH  -f  C6H5-  COC1  = 

AgCl  +  C7H50  •  NH  •  CH2-  COOH, 

which  is  found  to  the  extent  of  about  2^   in  the  urine 
of  oxen  and  horses,  and  sometimes  in  human  urine. 

It  will  be  observed  that  all  these  are  changes  which 
take  place  in  the  lateral  chain, 

(COOH),  (COC1),  (COKE2),  (CH2OH),  etc. 

806.  Other  substitutions  are  known  in  which  a  hydro- 
gen atom  has  been  replaced  in  the  benzene  nucleus  by  Cl, 
NO  2,  NH2,  etc.,  in  precisely  the  same  manner  as  in 
the  benzene  substitution  products.  For  example,  (1) 
Nitro  benzoic  acids  (o.  m.  p.),  C6H41S"O2  •  COOH,  are 
formed  when  benzoic  acid  is  treated  with  a  mixture  of 
KNO3  and  H2SO4  ;  and  (2),  these  are  reduced  by  nas- 
cent hydrogen  (Zn  -f-  HC1)  to  the  amido-benzoic  acids, 
(o.  m.  p.),  C6H4-  NH2,  COOH,  which  resemble  glycocine, 
but  which,  when  strongly  heated,  break  up  into  CO2 
and  aniline,  C6H5NH2.  The  ortho-amido-benzoic  acid 


440  ORGANIC  CHEMISTRY. 

is  known  as  anthranilic  acid,  and  may  be  obtained  by- 
oxidizing  indigo.  (3)  There  are  three  monochlor  ben- 
zoic  acids,  C6II4C1  •  COOII,  chlorbenzoic  (meta),  derived 
directly  from  benzole  acid  by  the  action  of  chlorine, 
chlorsalicylic  (ortho),  from  salicylic  acid  by  PC15,  and 
chlordracylic  (para),  from  para  chlortoluene. 

All  these  are  mono  derivatives  from  C6II5COOH,  and  contain 
the  residue  (C6H4COOH)/.  This  monovalent  radieal  may  be  united 
with  OH,  with  COOII,  with  CII3,  with  C6II5,  ami  similar  mono- 
valent groups  to  form  a  large  number  of  compounds  of  greater  or 
less  importance.  There  are  also  (//-derivatives  based  upon  the  res- 
idue (CgHgCOOH)",  as  di-chlor,  di-nitro,  nitro-chlor,  and  nitro- 
amido  benzole  acids,  each  with  its  own  series  of  salts  and  acids, 
and  each  is  isomeric  with  two  others;  and  there  are  numerous  other 
compounds  more  complex.  They  illustrate  the  wonderful  flexibil- 
ity of  the  benzene  nucleus,  as  well  as  the  j>ersistence  of  its  proper- 
ties amid  so  many  changes.  Among  these  are  those  that  follow. 

807.  Three  hydroxy-benzoic  acids  (o.  m.  p.)  are  known, 
C6II4*  OH,  COOII,  which  are  both  phenols  and  acids. 
Only  the  ortho  compound,  salicylic  acid,  is  of  importance. 

Salicylic  acid  occurs  free  in  spiraeas,  and  as  a  methyl 
ether  in  oil  of  wintcrgreen,  IK)  •  ('fiH-i'  COOCH3. 

It  has  recently  been  prepared  on  a  large  scale  (1)  by  heating 
phenol  and  caustic  soda  to  ISO0  --  sodium  phenate,  Ci;II5ONa;  and 
(2),  exposing  this  product  to  a  stream  of  carbonic  anhydride  until 
no  more  phenol  distils  over, 

2(C((H5ONa)  +  C02  --CJl"oH  -f  C6H4ONa     COONa; 

(3)  decomposing  the  residue,  which  is  di-sodium  salicylate,  with 
strong  HC1, 

C6II4ONa     C'OONa  -f  2IIC1  =  2NaCl  -f  CJI4     Oil,  COOII; 

and  (4),  finally  purifying  the  crude  acid  by  distillation  in  super- 
heated steam. 

Salicylic  acid  may  be  obtained  in  colorless  needles  and 
prisms,  which  melt  at  155°;  sp.  gr.,  1.48;  and  may  be 


THE  AROMATIC  ACIDS.  441 

sublimed,  but  which  at  higher  temperatures  partly  de- 
compose into  CO2  and  C6H5OH  =  phenol.  It  dissolves 
readily  in  alcohol,  very  sparingly  (-^W)  in  cold  water, 
but  more  readily  (y1^)  in  boiling.  Its  aqueous  solutions 
give  a  characteristic  violet  with  ferric  salts. 

The  free  acid  is  odorless,  and  has  an  astringent  taste. 
It  has  been  strongly  recommended  as  an  antiseptic  for 
food  preparations,  and  as  a  therapeutic  agent  in  acute 
rheumatism. 

Anisic  acid,  CH3O  •  C6H4  •  COOH,  the  isomer  of  the  oil  of  win- 
tergreen  is  methyl-paraoxy  benzoic  acid,  which  may  be  made  di- 
rectly from  anise  aldehyde,  and  obtained  in  fine  needles,  which 
melt  at  184°,  and  boil  at  280°. 

808.  Six  di-hydroxy  benzoic  acids,  C6H3(OH)2COOH, 
have   been   described.     One  of  these,  protocatechuic  acid 
(1:3:4),  requires  mention,  because   it  so  frequently  oc- 
curs as  one  of  the  decomposition  products  of  the  resins, 
balsams,   and   other   aromatic   compounds.     It   is   easiest 
obtained  from  tannins,  like  catechu,  by  (1)  melting  them 
with  KHO;  (2)  dissolving  the  fused  mass  in  hot  water; 
and  (3),  decomposing  the  potassium  salt  by  H2SO4.     It 
crystallizes  in  needles,  which   melt  at  199°,  and   decom- 
pose at  higher  temperatures  into  CO2  and  catechol. 

809.  Gallic    acid,    C6H2(OH)3COOH,    is   tri-hydroxy 
benzoic  acid.     It  occurs  in   the  leaves,  fruits,  and  bark 
of  many  plants,  as  tea,  sumach,  oak.    It  is  easiest  prepared 
(1)  by  fermenting  powdered  gall-nuts,  which  yield  gallo- 
tannic  acid ;    (2)    decomposing   this    product   by   boiling 
with  water;   and  (3),  recrystallizing.     It  forms  in  silky 
needles  (sp.  gr.,  1.7),  which  lose  at  120°  the  one  molecule 
of  water  of  crystallization  they  contain,  melt  at  222°,  and 
break  up  into  CO2  and  pyrogallol,  C6H3(OH)3.     It  is 
easily  oxidized,  and,  therefore,  reduces  the  salts   of  the 
noble   metals,  and  ferric   compounds  to  ferrous,  forming 
in   the    last   instance   a   bluish-black    precipitate,   which 


442  ORGANIC  CHEMISTRY. 

dissolves  in  excess  of  Fe2Cl6  with  a  greenish  color. 
When  heated  with  strong  1I2SO4,  it  yields  rujiyallic  acid 
(related  to  alizarin),  which,  when  mordanted  with  alum, 
yields  a  beautiful  red  dye. 

810.  The  tannins  are  substances  widely  distributed 
through  the  vegetable  kingdom,  and  are  characterized 
by  giving,  with  ferric  chloride  solution,  (1)  bluish-black 
precipitates  (gall-nuts,  tea-leaves),  or  (2),  greenish  pre- 
cipitates (catechu,  kino,  sumach,  oak-bark).  The  former 
class  are,  for  the  most  part,  glucosides  of  gallic  acid,  and 
consequently  yield,  on  dry  distillation,  jiynujdllol.  The 
latter  yield,  on  dry  distillation,  nyrocatechin,  and,  when 
fused  with  potash,  protocatechuic  acid  and  phloroglucin. 
The  tannins  resemble  each  other  strong!}*,  forming  yel- 
lowish amorphous  bodies,  easily  oxidized,  and  becoming 
brown  in  the  presence  of  the  alkalies,  coagulating  solu- 
tions of  gelatin,  and  having  a  marked  astringent  taste, 
especially  noticeable  in  green  fruits,  persimmons,  etc. 

The  ordinary  tannin  of  the  apothecary  is -prepared  by 
macerating  powdered  gall-nuts  for  several  weeks  in  a 
mixture  of  ether  and  dilute  alcohol.  On  filtering  this 
through  cotton -wool,  the  filtrate  separates  in  two  layers, 
the  upper  ethereal  layer  containing  gallic  acid  and  im- 
purities, the  lower  aqueous  portion  almost  pure  tannin. 
This  is  (jaUotannic  acid,  and  is  probably  the  first  anhy- 
dride of  gallic  acid,  2(C7II6O6)  —  II2O  =--- C14H10O9. 
This  sort  of  tanrtin  is  not  suited  for  making  leather,  but 
is  used  in  medicine  and  in  making  inks. 

Writing  fluids  arc  usually  made  by  digesting  a  mixture  of  gall- 
nuts  (2  parts),  ferrous  sulphate  (1  part),  and  gum  arable  (1  part), 
in  water  (10  parts)  for  many  days,  with  frequent  agitation.  Ferrous 
gallotannate  forms,  which  is.  prevented  from  settling  out  by  the  pres- 
ence of  tbe  gum.  Such  an  ink  will  appear  faint  when  first  used, 
but  rapidly  oxidizes  to  the  black  ferric  gallotannate.  The  black 
inks  contain  ferric  salts ;  copying  inks  an  addition  of  sugar.  The 
aniline  inks  are  merely  solutions  of  aniline. 


THE  AROMATIC  ACIDS.  443 

The  best  tannin  for  making  leather  is  obtained  from  oak,  birch, 
and  hemlock  barks.  The  hides  are  soaked  for  months  in  vats 
which  contain  water  and  the  ground  bark,  whereby  the  gelatin  of 
the  hide  becomes  coagulated"  throughout,  and  is  prevented  from 
putrefying  when  taken  out  and  worked  into  leather.  The  process 
is  a  mechanical  one,  and  the  result  may  be  attained  in  other  ways, 
as  by  a  mixture  of  alum  and  salt  (white  leather),  or  by  kneading 
with  oils  and  albumin  (chamois  leather). 

Caffe-tannic  acid,  from  coffee  berries,  yields  catechol  when  heated 
alone;  caffeic  acid,  CbH3(OH)2,  CH:CH  •  COOH,  when  boiled  with 
potash  lye;  and  protocatechuic  acid,  C6H3(OH)2COOH,  when  fused 
with  KHO.  It  gives  a  green  color  with  Fe2Cl6. 

811.  Cinnamic  acid,  C6H5  •  CH  :  CH  •  COOH,  occurs 
in   Peru,  tolu,  and   storax   balsams.     On   boiling  any  of 
these  with  soda  lye,  and  decomposing  the  sodium  cinna- 
mate    thereby  formed,  by  strong    IIC1,   the   free   acid   is 
obtained  in  inodorous  needles,  melting  at  133°,  and  dis- 
tilling at  300°;    sp.  gr.,  1.19.     It  yields  benzoic  acid  in 
most  of  its  reactions,  and  may  also  be  formed  from  ben- 
zoic aldehyde. 

Atropic  and  isatropic  acids,  which  are  formed  by  boiling  the  poi- 
sonous atropine  with  KHO,  are  isomers  of  cinnamic  acid,  and  may 
be  made  to  undergo  similar  transformations. 

812.  Coumaric  acid,  C6H4  •  OH,  CH  :  CH  •  COOH,  is 
made  from  coumarin,  which  exists  in  the  tonka  bean. 

It  may  be  made  artificially  by  boiling  together  sodium,  salicylic 
aldehyde,  and  acetic  anhydride,  C6H4  •  ONa,  CHO  +  (C2H3O)2O  = 
H2O  +  C2H3O2Na  +  C6H4,  (CH  :  CH  •  CO),  O  =  coumarin.  Longer 
boiling  with  alkalies  converts  the  coumarin  into  the  acid.  Both  are 
reduced  by  sodium  amalgam  to  hydrocumaric  acid,  C6H4  •  OH, 
CH2  •  CH2  •  COOH,  which  is  usually  obtained  from  sweet  clover. 
All  of  these  are  converted  by  fusion  with  KHO  to  salicylic  acid, 
C6H4  •  OH,  COOH,  and  are,  therefore,  ortho  compounds. 

813.  Tyrosine,  or  hydroxy-phenyl-amido-propionic  acid, 
C6H4-  OH,   CH2-  (CHNH2)  •  COOH,  sometimes  occurs 
ready  formed  in  old  cheese,  and  in  the  liver  and  pan- 


444  ORGANIC  CHEMISTRY. 

creas.  It  is  prepared  from  albuminoids  by  long  boiling 
with  acids  or  alkalies,  and  in  the  form  of  silky  needles, 
difficultly  soluble  in  water,  almost  insoluble  in  alcohol 
and  ether,  but  easily  soluble  in  acids  and  in  alkaline 
liquids  (§  730j. 

814.  The  other  aromatic  hydrocarbons  are  also  repre- 
sented by  numerous  series  of  acids:  (1)  Those  which 
contain  the  phenyl  radical  C6II5,  as  alpha  toluic  acid, 
C6H.  •  CH2-  COOII,  are  generally  made  by  boiling  their 
chlorides  first  with  potassium  cyanide,  and  then  with  pot- 
ash. These  acids  yield  benzole  acid  upon  oxidation.  (2) 
The  other  hydrocarbons,  [(C6II4/',  etc.],  when  treated 
with  dilute  nitric  acid,  oxidize  to  mono-basic  acids,  which 
arc  similar  to  bcnzoic  acids,  and  may  be  made  to  un- 
dergo similar  transformations.  For  example,  the  xylcnes, 
CCI14(CII3)2,  yield  o.,  m.,  and  p.  mono-basic  toluic  acids, 
C6II4  •  CT13,  COOII,  isomeric  with  alpha  toluic  acid; 
which  (3),  may  also  be  converted  by  oxidation  with  po- 
tassium permanganate  into  three  isomeric  dibasic  jththalic 
acids,  Cf(II4(COOH)2.  Phthalic  acid  (o.)  is  usually  made 
by  oxidizing  napthaline  dichloride  with  hot  dilute  nitric 
acid.  The  other  two,  isophthalic  (m.),  and  tcrephthalic 
(p.),  are  more  stable  and  arc  made  by  oxidizing  m. 
and  p.  xylenes  with  chromic  mixture;  but  all  are  so  fre- 
quently obtained  from  other  di-benzene  derivatives  that 
they  serve  as  guides  in  classifying  such  compounds  into 
ortho,  meta,  and  para  series.  The  members  of  such 
series  differ  in  crystalline  form,  solubility,  specific  grav- 
ity, melting  point,  etc.  Phthalic  acid  is  readily  soluble 
in  water,  and  crystallizes  in  shining  tables,  which  melt 
at  184°,  and  decompose  into  water  and  phthalic  anhy- 
dride, C6H4<£°>0. 

In  like  manner,  mesitylene,  one  of  the  tri -methyl  ben- 
zenes, C6H3(CH3)3,  yields,  successively,  mesitylenic  acid, 
C6H3(CH3)2COOH,  mesidic  acid,  C6H3CH3(COOH)2, 


THE  AROMATIC  ACIDS. 


445 


and  trimesic  acid,  C6H3(COOH)3;  all  of  them  sym- 
metrical (1:3:5).  A  remarkable  series  of  acids,  which 
are  structurally  derived  from  benzene  is  given  below; 

C6H5  •  COOH,  Benzoic  acid  from  benzene,  C6H5  •  H. 

C6H4  :   (COOH)  2,       Phthalic.  Lsophthalic,  Terephthalic, 

1:2.  1:3.  1:4. 

C6II3  :   (COOH)  3,       Heraimellitic,  Trimesic,  Trimellitic, 

1:2:3.  1:3:5.  1:2:4. 

C6H2  :   (COOH)4,      Mellophanic,  Prehnitic,  Pyromellitic, 

1:2:3:5.  1:2:4:5. 

C6H(COOH)5,             Wanting.  


C6  I   (COOII)6. 


Mellitic. 


H6     C6     (COOH) 6,  Hydromellitic. 

815.  Mellitic  acid,  C6-(COOH)6,  is  found  combined 
with  alumina  in  honey-stone,  a  mineral  sometimes  found 
in  coal  beds.  It  is  reduced  by  sodium  amalgam  to  hydro- 
mellitic  acid,  C12H12O12,  in  which  all  the  double  bonds 
of  the  benzene  chain  are  unlocked  by  the  entrance  of 
six  added  hydrogen  atoms,  H6  •  C6  •  (COOH)6.  These 
two  acids  are  sources  from  which  all  of  the  tetra  and 
tri  carboxylic  acids  of  the  above  table  are  obtainable. 

The  foregoing  are  only  a  small  part  of  the  oxygen  compounds 
known  which  contain  the  simple  benzene  nucleus.  Similar  com- 
pounds are  also  formed  from  the  conjugated  hydrocarbons.  For 
example,  'naphthalene,  C10H8,  when  oxidized,  splits  up  its  double 
ring,  and  yields  phthalic  and  oxalic  acids;  thus, 


C—  COOH      COOH 

+   I 
C— COOH      COOH 


HC 


Naphthaline. 


Phthalic  acid. 


Oxalic  acid. 


446  ORGANIC  CHEMISTRY. 

These   also    yield    a   great    variety   of    substitution    products    from 
which  may  be  formed  phenols,  quinones,  alcohols,  acids,  etc. 

Naphthalene,  when  treated  with  strong  1I2SO4,  yields  two  naph- 
thalene sulphonic  acids,  CJOH7SO2OH,  and  two  naphthalene  di- 
sulphonic  acids,  C10Ha(SO2OH)2.  These  are  sources  for  further 
substitution  products.  Each  of  the  first,  when  fused  with  caustic 
soda,  yields  a  naphthol,  C10H-OII;  with  sodium  formate,  a  naph- 
thoic  acid,  C,0H7  COOII,  for  which  an  aldehyde,  C'^H.  •  CHO, 
is  known,  but  no  alcohol,  Ci0IIT  •  CH2OII;  with  sodium  and  car- 
bonic acid,  an  oxy-naphthoic  acid,  C10IIf(  Oil  COOII.  The  di- 
sulphonic  acids  yield,  with  potassium  cyanide,  di-cyanides,  two 
naphthalene  carboxylic  acids,  C10II0(C(X)II)2,  and  the  like.  These 
coin])ounds,  as  well  as  those  derived  from  anthracene,  chrysene,  etc., 
will  be  sufficiently  mentioned  when  treating  of  their  products,  as 
the  mode  of  their  formation  is  similar  to  the  corresponding  ben- 
zene derivatives. 

816.  We  may  always  expect  numerous  substitution 
products  in  the  benzene  compounds,  and  frequently  may 
arrange  them  in  heterologous  series  containing  the  same 
nucleus,  but  which  replace  COOII  (acid)  for  COC1 
(chloride),  or  CONII2  (amide),  or  CII2OH  (alcohol), 
or  CIIO  (aldebyde),  etc.;  as,  phthalic  alcohol,  or  glycol, 
C6H4(CH2OH)2,  phthalic  chloride,  C6II4(COC1)2,  and 

phthalic   anhydride,    C6II4<^>O.     Where    there    are 

two  or  more  lateral  groups,  one  may  remain  unchanged 
and  give  rise  to  mixed  types,  like  the  alcoholic  benzoic 
acid,  (CH2OH) -CgH^COOH;  and,  finally,  the  nucleus 
may  suffer  furtber  substitutions,  and  give  rise  to  sucb 
compounds  as  nitro  phthalic  acid,  NO2C6H3(COOH)2 ; 
nitro  chlor -phthalic  acid,  NO2  •  C6H2C1  •  (COOH)2,  etc. 
The  next  page  contains  a  selection  of  compounds  taken 
from  the  "open"  and  the  "closed"  chains.  The  careful 
study  of  this  table  will  enable  the  student  better  to 
comprehend  the  relations  which  exist  among  organic 
substances. 


SERIES  COMPARED. 


447 


A  COMPAKTSON  BETWEEN  THE 

FATTY  SERIES  AND  AROMATIC  SERIES. 


CH4,  marsh  gas. 
CH3C1,  methyl  chloride. 
(CH3)X,  methyl. 
CH3NH2,  methyl  amine. 
CH3CN,  methyl  cyanide. 
CH3  •  CH3,  ethane,  di-methyl. 
(CH3  •  CH2)'  ethyl,  (C2H5)'. 

CH3  •  CH2OH,  ethyl  alcohol. 
CH3CHO,  aldehyde. 
CH3COOH,  acetic  acid. 
CH3COC1,  acetyl  chloride. 
(CH3CO)'  acetyl,  (C2H8O)X. 
(C2H3O)2O,  acetic  anhydride. 
C7H7  •  O    C2H3O,  benzyl  acetate. 
CH3  •  CONH2,  acetamide. 
(CH3)2CO,  acetone. 
CH2C1  •  COOH,  chlor-acetic  acid. 

CH2NO2COOH.  ? 
CH2NH2    COOH,  glycocine. 

CH3-  CHOH  •  COOH,  lactic  acid. 
CH2OH  •  CH2OH,  glycol. 

CH2(COOH)2,  malonic  acid. 
CH3  •  CH  :  CH  •  COOH,  crotonic 

acid. 
CH3  •  SO2OH,   methyl   sulphonic 

acid. 


C6II(1,  benzene. 
C6H5C1,  phenyl  chloride. 
(C6H5)',  phenyl. 
C6H5NH2,  phenyl  amine. 
C6II5CN,  phenyl  cyanide. 
C6H5CH3,  toluene,  methyl-phenyl. 
(C6H5CH2)'  benzyl,  (C7H7)'. 

(C7H7OH,  cresol. 

lC6H5-  CH2OH,  benzyl  alcohol. 
C6H5CHO,  benzaldehyde. 
C6H5COOH,  benzole  acid. 
C6H5COC1,  benzoyl  chloride. 
(C6H5CO)X  benzoyl,  (C,H5O)'. 
CVH5O)2O,  benzoic  anhydride. 
C2H5-  O  •  C7H5O,  ethyl  benzoate. 
C6H5CONH2,  benzamide. 
(C6H5)2CO,  benzophenone. 
C6H4C1  •  COOH,    chlor- benzoic 
acid. 

C6H4NO2COOH,     nitro  -  benzoic 

acid. 
C6H4NH2  •  COOH,    amido-ben- 

zoic  acid. 

C6H4OH  •  COOH,  salicylic  acid. 
C6H4  :  (CH2OH)2,    phthalic    al- 
cohol. 

C6H4(COOH)2,  phthalic  acid. 
C6H5-  CH:CH-  COOH,  cinnamic 

acid. 

C6H5  •  SO2OH,  benzene  sulphonic 
acid. 


Hippuric  acid,  C7H5O  •  NH  •  CH2  •  COOH,  benzoyl  glycocine. 


448  ORGANIC  CHEMISTRY. 


Recapitulation. 

The   derivatives   of    the    aromatic'    hydrocarbons    which    contain 
oxygen,  include,  among  other  compounds, 

(1)  HYDROXIDES   (OH)'.     Tlie  phen»h,  which   resemble  tertiary  al- 
cohols,  as  Cf,H)sOII,  and   also  weak   acids,   forming  salts,   like 
sodium  carbolate,  C6H5ONa. 

(2)  DI-OXIDES    (O2)".      The  Quinone*,    or   double    ketones    (CO)2//, 
including  the  important   anthraquinone,  C\-,H4  :  (C())2  :  C6H4. 

(3)  CARBOXYL  derivatives,  (COOHi.     The  Acids,  containing   from 
one  to  six  C'OOII   radicals,  and  thereby  forming  mono-basic  to 
hexa-basic  acids. 

(4)  SECONDARY    PRODUCTS   from  these  by  substitution  of  Cl,  CN, 
OH,   NO2,  S()2OH,  etc.,  for  II    in    the   carbon   nucleus,  which 
are  also  phenols,  quinones,  and  acids. 

(5)  THE  SALTS  and  ETHERS  of  the  foregoing,  with  metals  and  alkyl 
radicals. 

(6)  THE    REDUCTION    PRODUCTS    from     acids,    including    Alcohols, 
(CH2OII)',  aldehyde*,  (CIIO)',  and 'hydrocarbons  (CH)6. 

(7)  COMPLEX  SUBSTANCES,  which   may   include   radicals    from    any 
one  of  these,  or  from  any  one  of  the  fatty  series,  bound  to  one 
or  more  oxy-benzene  groups. 

(8)  THE  NITRO  (NO2)  and  sulphonic  (SO2OH)  derivatives  are  of 
great  use  in  metathetical  operations. 


CHAPTEE    XXVIII. 

AROMATIC    SUBSTANCES    CONTAINING    NITROGEN. 

817.  When  nitric  acid  acts  upon  organic  bodies  (1)  it 
unites  directly  with  basic  substances,  like  aniline,  forming 
salts;  as,  C6H5NH2HNO3,  aniline  nitrate.  (2)  It  forms, 
with  the  alcohols,  ethereal  salts;  as,  C2H5OH-fHNO3= 
H2O-|-C2H5NO3,  ethyl  nitrate.  Both  classes  of  these 
salts  are  easily  decomposed  by  caustic  potash. 

(3)  Dilute   nitric  acid   is  used   as  an   oxidizing   agent 
when    only   a   moderate   action    is   allowable,  as   in   the 
preparation  of  phthalic  acid. 

(4)  All  aromatic  compounds,  when  poured  into  strong 
nitric    acid,    form    "nitro"   substitution    compounds,    ex- 
changing  from  one  to  three  atoms  of  hydrogen   in  the 
benzene  nucleus   for  an    equal   number  of  nitryl   groups. 
At  low  temperatures,  the  product  is  ordinarily  a  mono- 
nitro  derivative;  as,  C6H5NO2.     The  di-,  C6H4(NO2)2, 
and  tri-,  C6H3(NO2)3,  nitro  derivatives  usually  require 
the  use  of  a  mixture  containing  the  strongest  nitric  acid 
with  twice  its  volume  of  strong  sulphuric  acid. 

When  the  substance  has  been  dissolved  by  the  acid,  the  entire 
mixture  is  poured  into  a  large  quantity  of  water  to  remove  the 
excess  of  acid,  etc.  The  nitro-derivatives  settle  out  as  yellow  or 
reddish  substances  which  are  sometimes  liquids,  but  more  frequently 
crystallizable  solids.  These  nitro  compounds  are  not  decomposed 
by  boiling  with  potash  lye,  and,  as  a  class,  are  far  more  stable 
than  the  nitro  compounds  of  the  fatty  series. 

Only  a  few  have  any  direct  application  in  the  arts  ;  but  these 
are  manufactured  in  enormous  quantities  in  the  preparation  of  the 

so  called  coal-tar  dyes,  aniline,  alizarine,  and  their  derivatives. 
Chem.— 29.  (449) 


450  ORGANIC   CHEMISTRY. 

818.  Mono-nitro  benzene,  C61I5XO2,  is  also  used  under 
the   name   of  the  ''essence   of  jnirbane,"  as   a   substitute 
for  the  oil  of  bitter  almonds.     It  is  a  poisonous,  yellow 
fluid,  which  solidifies  at  :>°,  and  boils  at  210C;  sp.  gr.,  1.2. 

The  ordinary  di-nitro  henzent'.  (\.II4(XO2)2,  is  the  met  a 
modification,  a  solid,  easily  soluble  in  hot  alcohol,  and 
crystallizing  from  such  solutions  in  thin  rhombic  plates, 
which  melt  at  90°.  The  ortlio  compound  melts  at  118°, 
the  para  at  172°.  It  may  be  noted  that  para  derivatives 
have  generally  the  highest  melting  points. 

Tri-nitr<>  />/'/«crw.  C6II3(XO2)3  (symmetrical),  requires 
for  its  formation  the  mixture  of  the  strongest  acids,  and 
long  heating.  It  crystallizes  from  its  alcoholic  solution 
in  white  leaflets,  which  melt  at  122°.  and  easily  sublime. 

These  may  be  taken  as  types  of  the  simple  nitro  derivatives. 
The  methyl  homologues,  as  nitro  toluene,  CCII4  NO2,  ('H3,  nitro 
xylene,  C,,H3  NO.,,  (CHa)2,  etc.,  resemble  them  in  their  chemical 
reactions,  but  are  not  poisonous. 

An  enormous  number  of  nitro  compounds  are  known  which  con- 
tain, besides  the  NO2  group,  other  radicals.  The  most  important 
of  these  are  the  nitro-haloid,  containing  Br  or  ( '1  attached  to  the 
benzene  nucleus;  as,  Cl  C,,II4  NO2 ;  the  nitro  phenols,  which 
contain  hydroxyl ;  as,  C(,II,  X()2,  Oil,  and  the  nitro-sulphonic 
acids,  which  contain  the  group  SO2OII,  as  nitro-phenol-sulphonic 
acid,  IK)  CCII.,  NO2,  SO,OII. 

819.  Reducing  agents  convert  nitro  compounds  to  amido 
derivatives,  in  which  "amidogen"  (XII2)'  replaces  II  in 
the  benzene  nucleus;   as,  C6II5  •  XII 2  =  amido  benzene. 
This  reduction  may  be  effected  by  the  action  of  nascent 
hydrogen,  obtained,  c.  g  ,  by  first  mixing  the  nitro  com- 
pound with  strong  IIC1,  and  then  adding  tin  or  SnCl2 ;  as, 

C6H5  •  XO2  +  6HC1  +  3Sn  = 

2H2O  +  3SnCl2-f  C6H5XH2;  then  (2), 
C6H5  •  N02  +  6HC1  +  3SnCl2  = 

2H2O  +  3SnCl4  -f  C6H5  •  NH2. 


ANILINE.  451 

The  product  dissolves  in  excess  of  HC1  to  form  hydro- 
chlorides;  as,  C?H5  •  NH2HC1. 

In  di-  or  tri-nitro  derivatives,  a  partial  reduction  results 
in  the  formation  of  nitro-amido  compounds;  as,  from 
C6H4:  (NO2)2  may  result  NO2  •  C6H4  •  NH2. 

820.  The  first  of  these  amido  compounds  is  ANILINE, 
or  phenylamine,  C6II5NII2.  The  higher  members  of  this 
series,  toluidine,  CII8  •  C6II4,  NH2,  etc.,  are  metameric 
with  the  series  of  amines  derived  from  the  chlorides 
of  the  aromatic  alcohols  by  the  action  of  ammonia;  as, 
C6H5CH2C1  +  NH8  ==  HC1  +  C6H5CH2KET2  =  benzyl 
amine,  which,  however,  contain  the  NII2  group  in  the 
lateral  chain.*  The  benzylamine  series  are  freely  sol- 
uble in  water,  and  yield  solutions  which  resemble  those 
of  the  caustic  alkalies.  The  members  of  both  series 
are  strong  bases,  and  unite  directly  with  acids  to  form 
salts,  like  those  of  ammonia.  The  members  of  the  an- 
iline series  are  but  sparingly  soluble  in  water.  Their 
salts  yield,  by  treatment  with  nitrous  acid,  "azo"  and 
"diazo"  compounds,  p.  453;  as,  C6H5  •  NH2,  HNO^=an- 
iline  m£rate  +  HNO2  =  2H2O-fC6H5  •  N2  •  NO3  =  diazo- 
benzene  nitrate. 

Aniline  is  so  named  because  it  was  first  derived  from 
indigo  (Arabic,  Annil).  It  is  now  manufactured  in  enor- 
mous quantities  by  reducing  mono-nitro  benzene  with 
iron  filings  and  acetic  acid.  The  aniline  salt  which  forms 
is  decomposed  by  chalk,  and  the  aniline  distilled  off  by 
the  aid  of  steam. 

Aniline  is  a  colorless  liquid,  which  gradually  becomes 
brown  when  exposed  to  the  air;  sp.  gr.,  1.036;  solidify- 
ing in  freezing  mixtures,  then  melting  at  — 8°,  and 
boiling  at  184°.  It  dissolves  readily  in  alcohol,  and  in 
about  32  parts  of  water  at  16°.  This  solution  (1)  colors 


*The  series  of  pyridine  bases,  page  461,  contain  pseudo  isomers  of  these: 
as,  picoline,  NC6H4  •  CHS. 


452  ORGANIC  CHEMISTRY. 

a  pine  shaving  yellow,  (2)  forms  with  a  few  drops  of  cal- 
cium hypochlorite,  a  purple  violet  color,  mauve. 
Aniline  enters  into  a  great  variety  of  compounds: 

I.  By  direct  addition,  (a)  with  acids  to  form  salts  which 
are    generally   soluble    in    water;    as,   (C6H7N)2H2SO4, 
aniline  sulphate;    (b)  with  certain   metallic  salts  to  form 
double  Halts,  like  the  platinochloride,  (C6H7N)2PtCl4. 

II.  (fl)  By  substitutions  in  the  amido  group  with  alkyl 
radicals    by    heating    aniline    with    methyl    iodide,    etc., 
forming  secondary  and   tertiary  derivatives,  like  methyl 
aniline',    C6II6NI1CII3.    and,    C6II6X(CII8)2,    di-methyl 
aniline,  etc.     It  is  worth  while  to  notice  that  these  com- 
pounds, when  heated  strongly  in  closed  vessels,  are  con- 
verted  to   the    primary   bases,   which    are   isomeric  with 
them,  methyl  aniline  becoming  toluidinc,  OII3'C6II4'NH2, 
and    di-methyl    aniline   becoming,   (CII3)2  :  C6II3  •  NII2, 
xylidene. 

(b)  The  anilides  arc  generally  obtained  by  the  action 
of  an  acid  chloride  upon  aniline;  as,  C2II8OC1,  acetyl 
chloride  -f  C6II5NII2=  IIC1  +  C6H6-  Nil  •  C2H3O  =  acet- 
anilide.  These  are  stable  bodies,  decomposed  only  after 
long  heating  with  potash  lye.  Acetanilide  forms  color- 
less lamina4,  which  melt  at  112°,  and  volatilize  at  295°. 

III.  By   substitution    within   the   benzene    nucleus   by 
which   monovalent  radicals,   like   Cl,  Br,  NO2,   SO2OII, 
replace  from  one  to  five   hydrogen  atoms,  forming  com- 
pounds, like  the  three  mono-chlor  anilines,  C6H4.C1,NH2, 
the   three  mono-nitro  anilines,  C6H4  •  NO2NH2.     These 
changes  are  effected  in  various  ways,  frequently  by  the  di- 
rect action  of  Cl.  Br,  and  of  the  fuming  acids  upon  aniline. 
The  basic  character  of  aniline  disappears  either  wholly 
or  in  part  with  the  entrance  of  these  negative  radicals. 

IY.  Finally,  aniline  derivatives  4iave  been  described 
which  represent  two  or  more  of  these  groups. 

The  methyl  derivatives  of  aniline  are  its  homologues  toluidine, 
CH3  •  C6H4  •  NH2;  xytidine,  (CH3)2  :  C6H3  •  NH2 ;  mesidine, 


AZO  COMPOUNDS. 


453 


(CH3)3  -  C6H2  •  NH2,  etc.,  including  their  numerous  isomers. 
They  are  formed  by  reduction  of  the  nitro  derivatives  of  their  hy- 
drocarbons, and  exhibit  analogous  properties  to  those  of  aniline. 

821.  THE  AZO  AND  DIAZO  COMPOUNDS  contain  two  ni- 
trogen atoms,  N  •  N,  linked  together,  and  are  named 
from  azote,  the  French  word  for  nitrogen.  The  follow- 
ing are  examples  of  the  structural  formula?  of  both. 


Azo. 

DIAZO. 

CeH5 
C«H5 

•  N 

I  >c 

•  N 

)  Azoxybenzeue. 

C6H5 
NO 

N 

^ 

Diazobenzene  nitrate. 

C6H5 
C6H5 

•  N 
II 

•  N 

Azobenzene. 

C6H5 
HO 

N 

Ur 

Diazobenzene  hy- 
droxide. 

C6H5 
C6H5 

•  NH 

•  in 

Hydrazobenzene. 

C6H6  • 
H 

NH 

u 

Phenyl  hydrazin. 

The  azo  compounds  are  intermediate  between  the  nitro  and 
amido  derivatives  of  the  aromatic  hydrocarbons,  and  may  be  ob- 
tained by  the  partial  reductions  of  the  former,  or  by  correspond- 
ing oxidations  of  the  latter.  For  example,  if  sodium  amalgam  is 
added  to  a  solution  of  nitro  benzene,  2(C6H5NO2),  in  alcohol, 
there  will  be  produced  in  succession,  azoxybenzene,  C12H10N2O; 
azobenzene,  C12H10N2;  hydrazobenzene,  C12H12N2;  and,  finally, 
aniline,  2(C6H7N2).  The  hydrazo  compounds  are  colorless;  the 
azo  and  azoxy,  red  or  yellow.  Only  the  azo  compounds  can  be 
distilled  without  decomposition;  all  these  yield  substitution  prod- 
ucts with  Cl,  HNO3>  etc. 

822.  The  diazo  compounds  are  unstable  bodies,  often 
violently  explosive  when  heated  or  struck,  and  very 
readily  breaking  up  under  the  influence  of  various  re- 
agents. Diazo  salts  are  produced  when  nitrous  acid  is 
made  to  act  upon  salts  of  those  amido  derivatives  which 
contain  the  NH2  group  in  the  benzene  nucleus ;  as, 

C6H5-NH2,  H2SO4  =  aniline  sulphate  +  HNO2  = 

2H2O  +  C6H5  •  N2  •  HSO4  ==  diazo  benzene  sulphate. 


454  ORGAXTC  CHEMISTRY. 

Great  attention  has  recently  been  paid  to  these  com- 
pounds, both  by  reason  of  the  easy  substitutions  they 
admit,  and  for  the  brilliant  and  durable  dyes  produced 
by  their  various  combinations. 

As  examples  of  these  we  may  study  the  diazobcnzcne  sulphate.  (1) 
If  boiled  with  water,  it  breaks  up  into  II_,S(),  :  N"2,  and  C'f,II,,()H 
phenol.  (~)  If  treated  with  KI  it  forms  phenyl  itxlidc,  C6II5I.  (3)  If 
heated  with  aniline,  diazo-timido  benzene  forms  Of>II,,  •  N2  NH(C6H5), 
wliieh  is  gradually  converted  in  the  presence  of  a  small  amount  of 
an  aniline  salt  into  its  isomer,  CRllr,  N2  C6H4NII2  -  amulo  azo- 
bcnzcne,  which  is  the  dve  known  as  aniline  yellow. 

X<i])hthylamine,  C'j0II7NII2,  yields  analogous  products.  (1)  When 
heated  with  UNO,  it  forms  di-nitro  haphthol,  whose  sodium  salt, 
C10H5(NOa)2ONa,  is  the  brilliant  naphthalene  yellow.  (2)  On  pass- 
ing NO2  into  its  warm  alcoholic  solution,  an  aniido-azo  naphth- 
aline forms,  which,  on  subsequent  heating  with  additional  naph- 
thylamine,  forms  C,0II7  Nil  C'lo^ti  '  ^2  '  ^-'IO^T»  which  yields 
the  dye  known  as  magdalfi  red. 

823.  THK  AROMATIC  iiYDRAZiNs  are  bases,  slightly  sol- 
uble in  water,  easily  in  alcohol,  and  are  either  solids, 
having  a  low  melting  point,  or  are  oily  liquids.  They 
are  obtained  by  reduction  of  the  diazo  compounds.  Nas- 
cent hydrogen  reduces  diazo-amido-benzol  to  aniline  and 
phenyl  hydrazin;  thus, 


Phenyl  hydrazin,  C6H8N2,  is  a  colorless  oil,  solidified 
by  cold  to  tabular  crystals.  It  is  easily  oxidized,  and  is, 
therefore,  a  good  reducing  agent.  When  added  to  Fehl- 
ing's  solution,  it  precipitates  even  without  warming,  the 
red  Cu2O,  and  is  changed  to  aniline  and  benzene.  This 
test  may  be  used  for  other  hydrazins,  and  also  indi- 
rectly for  the  diazo  compounds  from  which  they  may 
be  formed.  The  nitroso  hydrazins  obtained  by  treating 
hydrazin  salts  with  KXO2,  when  mixed  with  any  phenol 
and  strong  H2SO4,  produce  a  series  of  fine  colors,  — 
brown,  green,  and  finally  blue. 


ANILINE  DYES.  455 


ANILINE  DYES. 

824.  The  crude  aniline,  which  is  used  in  making  an- 
iline colors,  contains  a  large  percentage  of  para  and 
ortho  toluidine,  CII3  •  C6II4  •  NII2.  The  red  dyes  can  not 
be  made  from  pure  aniline.  The  first  discovered  of  these 
dyes,  Mauve,  is  prepared  by  oxidizing  aniline  sulphate 
with  potassium  bichromate.  It  contains  the  base  mau- 
vein,  C27II24X4,  which,  when  united  with  various  acids, 
yields  the  purple  noticed  in  testing  for  aniline  with  chlo- 
ride of  lime. 

The  most  important  of  these  red  dyes  is  made  by 
heating  crude  aniline  with  arsenic  acid  (As2O5)  to  140°. 
On  dissolving  the  residue  in  dilute  hydrochloric  acid, 
and  adding  common  salt,  C20II19N3,  IIC1,  rosaniline 
hydrochloride,  precipitates.  This  salt,  known  as  fuchsine, 
on  being  dissolved  in  hot  water,  yields,  on  the  addition 
of  ammonia,  a  colorless  precipitate  of  C20H21N3O,  which 
is  generally  considered  as  the  hydrate  of  the  base  ROS- 
ANILINE,  C00H19N3,  which  was,  perhaps,  formed  thus: 


CH3-  C6H4- 
:C     C6H3-CH3 

3H2O-f  2(C6H4  NH2)  !  =rosaniline. 

NH. 

Other  salts  of  rosaniline,  with  HNO3  and  C2H4O2,  are  also  sold 
as  fuchsine,  and  are  obtained  in  splendid  gold-green  crystals,  readily 
soluble  in  alcohol  to  a  beautiful  red  color.  They  dye  wool  and 
silk  red  without  the  addition  of  mordant  (1  part  fuchsine  to  200 
wool).  Numerous  interesting  and  valuable  dyes  have  been  pre- 
pared from  rosaniline  salts;  as, 

Aniline  blue,  C20H16(C6H5)3N3HC1,  by  heating  fuchsine  with 
excess  of  aniline. 

Hofmann's  violet,  C20H16(C2H5)3N3HC1,  by  heating  an  alcoholic 
solution  of  fuchsine  with  ethyl  iodide. 

Aniline  green,  C20H14(CH3)5N3HC1,  by  heating  fuchsine  with 
methyl  iodide  and  methyl  alcohol. 

Fuchsine,  warmed  with    sulphuric   acid,  yields   sulphonic   acids. 


456  ORGANIC  CHEMISTRY. 

The  mono  sulphonic  acid,  when  converted  to  its  sodium  salt,  is  the 
Nicholson's  blw,  C38II  ,0N3SO2OXa,  used  in  wool  dyeing. 

Aldehyde  green,  C_, 2H27N3S2O,  is  formed  by  reducing  aniline 
blue  sulphonic  acids  by  aldehyde. 

Aniline  black,  (C30H25NS),  forms  when  aniline  hydrochloride  is 
oxidized  by  potassium  chlorate  in  presence  of  certain  metallic  salts, 
as  CuCl2.  The  metals  appear  to  act  as  "carriers  of  oxygen,"  being 
alternately  reduced  and  oxidized.  The  best  blacks  are  obtained 
with  salts  of  vanadium,  one  part  of  vanadium  sufiicing  for  270,000 
parts  of  the  aniline  salt. 

THE  INDKJO  (Jiiorr. 

825.  The  juices  of  many  plants  contain  a  colorless  glu- 
coside,  named  indium,  which  decomposes  when  boiled 
with  dilute  acids  into  a  sweetish  substance,  indiglucin, 
and  indigo  blue;  thus,  2(C26H81NO17)  indican-\-4H.2O  = 
<)((/<;lI  j  0O6)  indiglucin  -f-  C,  6 II  j  0N2()0,  indigo  blue.  The 
indigo  of  commerce  is  prepared  from  the  Indigofera, 
etc.,  by  macerating  their  leaves  in  water,  whereby  a  fer- 
mentation is  set  up  which  decomposes  the  indican,  and 
also  yields  indigo  white,  C-16II12X2()0.  which  dissolves. 
The  liquid  is  then  drawn  oft*  into  shallow  vessels,  and 
is  brought  by  stirring  and  boating  into  contact  with  the 
air  as  much  as  possible.  This  oxidizes  the  indigo  white 
to  indigo  blue,  which  is  allowed  to  settle,  and  is  then 
washed  and  dried.  • 

Baeyer  has  succeeded  in  the  synthetical  preparation  of  indigo 
blue.  His  actual  process  consists  (1)  in  converting  toluene  to  cin- 
namic  acid  (p.  443);  (2)  nitrating  this  to  orth-nitro  cinnamic  acid, 
CCH4  •  NO2  •  CH  :  CH  •  COOH;  (3)  forming  by  action  of  bromine, 
C6H4NO2  •  CHBr  •  CHBr  •  COOH,  ortho-nitro-dibrom-cinnamic 
acid.  (4)  When  this  is  treated  with  sodium  hydroxide,  and  the 
product  decomposed  by  an  acid,  ortho-nitro  phenylpropionic  acid 
forms  C6H4NO2  '  C  :  C  COOH.  (5)  This,  when  reduced  by  nas- 
cent hydrogen  or  glucose,  yields  indigo  blue. 

CO      C     NH 

C6H4<  ||  >CCH4. 

NH     C      CO 


THE  INDIGO   GROUP.  457 

826.  Indigo  blue  is  quite  insoluble  hi  water  or  alcohol, 
but  dissolves  without  decomposition  in  concentrated  sul- 
phuric acid,  forming,  in  the  first  instance,  indigo  mono- 
sulphonic    acid,    C16H9N2O2(SO2OH),    but   passing,   on 
warming,     into     C16H8N2O2(SO2OH)2,     sulphindigotic 
acid.     This   may  be  completely  removed  from  its  dilute 
solutions  by  clean  white  wool  (Berlin  blue).     Its  potas- 
sium salt  is  a  valuable  blue  dye  sold  as  indigo  carmine. 

Reducing  agents  in  the  presence  of  alkaline  liquids  convert  in- 
digo blue  to  indigo  white,  C16H10N2O2  +  H2  =  C16H12N2O2,  which 
dissolves,  but  may  be  precipitated  in  white  flocks  by  neutralizing 
with  an  acid.  These  are  rapidly  reconverted  to  the  blue  on  oxida- 
tion. Woolen  fabrics,  steeped  in  such  alkaline  solutions,  absorb 
the  coloring  matter,  and  afterwards,  on  exposure  to  the  air,  are 
dyed  of  a  permanent  blue  by  the  formation  of  indigo  blue  within 
the  tissue. 

Oxidizing  agents  convert  indigo  blue  to  isatin, 

C16H10N202  +  Oa  =  C16H10N204,  or  2 

If  the  oxidizing  action  is  carried  too  far  other  products  are  formed. 
For  example,  with  H2O-|-C1,  etc.,  chlorisatin,  C8H4C1NO2,  di-chloris- 
ntin,  C8H3C12NO2,  etc.  Isatin  dissolves  freely  in  hot  water,  and 
crystallizes  on  cooling  in  yellowish-red  prisms.  The  solution  in 
alcohol  colors  the  skin  yellow  and  produces  with  it  a  persistent 
disagreeable  odor. 

Reducing  agents  (as  P  in  PC15)  may  reconvert  isatin  to  indigo 
blue,  but  usually  they  act  by  adding  hydrogen.  Nascent  hydrogen 
in  acid  liquids  produces  isatyde,  C16H12N2O4;  in  alkaline  liquids, 
dioxindol,  C16H14N2O4  ;  then  oxindol,  C8H7NO2,  which,  when  heated 

pTT 

with  powdered  zinc,  yields  indole,  C8H7N  =  C6H4<^g>CH;    and 

skatole,  C9H9N.  Both  of  these  are  ill-odored  compounds  which  also 
occur  in  human  excrement,  and  may  be  obtained  from  albumin  by 
melting  with  KHO,  or,  better,  by  digestion  with  the  pancreatic 
juice.  So  also,  in  the  urine  of  mammals,  a  substance  similar  to 
indican  sometimes  occurs  which  colors  the  liquid  blue  on  exposure 
to  the  air. 

827.  Several  groups  of  the  dye-stuffs  have  been  men- 
tioned in  the  preceding  pages.     The  student  will  notice 


458  ORGANIC  CHEMISTRY. 

(1)  that  the  parent  substances  are  colorless,  or  nearly 
so,  as  phenol,  benzene,  aniline;  (2)  that  the  tinctorial 
power  enters  with  certain  groups,  as  NO2  in  picric  acid 
or  CO  in  alizarine;  (3)  that  other  complex  groups,  like 
the  tri  phcnyl  methane,  (C6H5)3CII,  in  fuchsine,  are 
also  required  as  '-salt  builders;*'  (4)  that  frequently  the 
free  base  is  also  colorless,  as  in  rosaniline,  and  that  the 
dye-stuff  is  either  manifested  only  in  salts,  or  becomes 
intensified  when  they  are  formed;  (5)  that  substances  of 
similar  composition  exhibit  similar  colors,  as  rosaniline 
and  rosolic  acid;  picric  acid  and  trinitraniline. 

828.  The  first  of  the  coal-tar  colors,  main-e,  was  discov- 
ered in   1856,  and  lias  been  followed  by  a  large  number 
of  brilliant  dyes,  which    have   largely   supplanted    those 
then  in  use.     The  latter  are  cither   of  inorganic  origin 
as  Scheele's  green,  or  are  derived    from   certain    plants 
or  from  the  animals  that  feed   upon  them.     Many  of  the 
vegetable  colors  are  NO  delicate  and  evanescent  that  they 
can  not  be  employed   in  the  arts;   such,  for  example,  is 
the  chlorophyll,  or  leaf-cjrcen.     This  is  found,  together  with 
protoplasm,   in   all   the  growing  cells  of  plants  exposed 
to  sunlight,  and  appears  to  contain  a  blue  coloring  mat- 
ter (cyanine),  a  yellow  (xanthine},  and  a  trifling  amount 
of  iron,  but  its  chemical  composition  is  unknown. 

The  vegetable  dye-stuffs  are  generally  produced  from 
colorless  glucosides,  which  are  decomposed  by  fermenta- 
tion, or  by  boiling  with  dilute  acids,  as  already  men- 
tioned in  the  preparation  of  indigo  and  alizarine.  The 
coloring  matters  thus  obtained  are  themselves  frequently 
almost  colorless,  and  first  take  on  a  decided  color  when 
treated  with  certain  re-agents  known  as  mordants. 

829.  Besides  the  dyeing  materials  already  considered 
the  following  require  mention,  and  are  placed   here,  al- 
though they  do  not  contain  nitrogen : 

Anatto.  obtained    from    the   fruit  of    Bixa  Orelana.,  as   an  orange 


DYE-STUFFS.  459 

paste,   is   used    in   coloring   butter   and   cheese.     It   contains   bixine, 

t;28H34O5. 

The  orange-yellow,  saffron,  comes  from  the  dried  flowers  of  crocus 
sativa,  as  a  glucoside  of  an  agreeable  odor.  It  contains  crocine, 
C16H1806. 

The  safflower,  carlhamus  tinctorius,  contains,  C24H30O15,  a  yellow 
dye,  soluble  in  water  and  a  red  dye,  C14H16O7,  carthamine,  which 
is  used  as  a  cosmetic. 

Turmeric  is  extracted  from  the  roots  of 'the  curcuma  longa,  by 
boiling  with  benzene.  The  coloring  matter  is,  C14H14O4,  curcu- 
rnine,  which  dissolves  in  alkalies  with  a  brownish-red  color.  Tur- 
meric paper  is  prepared  from  its  solution  in  alcohol.  When  this 
is  moistened  with  boracic  acid,  and  then  dried,  it  becomes  orange- 
red,  which  changes  to  blue  on  adding  an  alkali. 

Fustic  is  a  yellow  dye  made  from  the  wood  of  the  morus  tinc- 
toria.  It  contains  morine,  C12H10O6,  and  maclurine,  C13H10O6. 
The  alcoholic  solution  of  each  is  colored  green  by  ferric  chloride. 

Brazil  wood  is  employed  in  making  red  ink.  It  contains  braz- 
tfine,  C16II14O5  -f-  H2O,  which  is  of  a  pale  amber  color,  becoming 
a  red  upon  oxidation,  or  when  dissolved  in  alkalies. 

The  Logwood  extract  is  made  from  the  heartwood  of  the  Hcem- 
ntoxylon  campechianum.  Its  coloring  power  is  due  to  hcematoxyline, 
C16H14O6,  3H2O,  which,  when  first  prepared,  is  quite  colorless,  but 
reddens  in  the  sunlight.  It  dissolves  in  ammonia  with  a  purple- 
red  color,  which  rapidly  darkens  from  the  formation  of  hcemateine, 
C16H12O6.  The  solution  of  logwood  extract  yields  a  red  lake 
with  alum  solution,  a  dark  violet  lake  with  ferric  salts,  and  a  deep 
black  with  potassium  chromate.  These  are  extensively  used  in 
inks,  and  in  producing  browns  and  blacks  upon  cotton. 

The  cochineal  and  lac  dyes  are  due  to  insects  of  the  coccus  family. 
The  former  contains  carminic  acid,  C17H18H10,  which  is  a  gluco- 
side,  yielding  carmine  red,  C^H^O;,  soluble  in  water  and  alcohol. 
The  commercial  carmine  of  this  is  a  lake,  prepared  by  boiling  the 
pulverized  insects  with  water  and  precipitating  with  alum.  The 
ammoniacal  solution  is  used  as  a  red  ink. 

The  famous  royal  purple  of  the  ancients  was  obtained  from  mol- 
luscs of  the  murex  tribe. 

830.  The  art  of  the  dyer  consists  partly  in  imparting 
to  a  fabric  the  color  desired,  and  partly  in  rendering  it 
fast;  that  is,  insoluble,  so  as  not  to  be  destroyed  by 
washing.  Some  fibers,  notably  wool  and  silk,  absorb 


4GO  ORGANIC  CHEMISTRY. 

nitrogenous  coloring  matters  directly,  and  require  only 
an  immersion  in  the  hot  dye-beck.  Tissues,  like  linen 
and  cotton,  must  be  first  mordanted,  —  that  is,  treated 
with  solutions  of  the  salts  of  tin,  iron,  alumina,  etc.,— 
and  afterwards  be  soaked  in  the  alkaline  solutions  of  the 
coloring  matters  employed.  This  treatment  produces 
within  the  fiber  of  the  cloth  a  lake,  which  has  a  color 
due  partly  to  the  dye-stuff,  and  partly  to  the  mordant, 
and  which  is  fixed  by  "ageing.''  This  is  attained  by 
exposing  the  cloth  either  to  the  air  or  in  chambers  filled 
with  steam.  In  some  dyes,  the  color  is  made  by  purely 
chemical  reactions ;  thus,  if  a  piece  of  cloth  is  soaked  in 
a  solution  of  ferric  chloride,  and  afterwards  in  one  of 
potassium  ferrocyanide,  Prussian  blue  will  be  formed, 
and  impart  a  fast-blue  tint  to  the  fabric. 

831.  The  art  of  the  calico-printer  consists  in  producing, 
upon  the  natural  white  of  bleached  and  cleansed  cotton 
goods,  patterns  in  one  or  more  colors.  If  but  one,  he 
may  produce  a  design  in  white  or  the  converse  by  print- 
ing it  before  dyeing  (I)  with  "resists"  (acids  that  de- 
compose the  mordants,  citric,  phosphoric,  etc.),  or  (II), 
with  "discharges''  (substances  that  prevent  the  absorp- 
tion of  the  dye,  as  soap  or  grease,  or  that  bleach  it,  as 
copper  acetate  in  indigo  printing);  but  (III),  the  usual 
process,  known  as  the  madder  style,  and  also  applicable 
for  many  shades  and  colors,  consists  (1)  in  printing  the 
design  upon  the  cloth  by  a  sufficient  number  of  en- 
graved rollers,  each  smeared  with  the  appropriate  mor- 
dant, previously  thickened  by  starch  or  gum.  (2)  The 
excess  of  the  mordant  is  now  removed  by  "cleansing" 
with  hot  water  and  cows'  dung,  or  dung  substitutes,  like 
acid  sodium  phosphate  or  arseniate.  (3)  The  goods  are 
now  boiled  in  a  large  vat  containing  the  dye-stuff  sus- 
pended or  dissolved  in  water,  and  then  (4),  washed  to 
remove  the  dye  from  the  unmordanted  portions.  (5) 
The  goods  are  now  finished  by  "ageing." 


ORGANIC  BASES.  461 


ORGANIC  BASES. 

832.  The  pyridine  bases,  CnHn_5N,  are  produced  when- 
ever  complex   nitrogenous   compounds   are   subjected   to 
dry  distillation.     They   are,    for   the    most    part,    bitter, 
poisonous  substances,  having  a  peculiar,  penetrating  odor. 
Pyridine,  C5II5N,  which  is  the  first  of  the  series,  may  be 

,   PTT PTT    \ 

represented   by  a  closed  chain,  CH\  QJJ_CIJ /^>  in 

which  a  single  nitrogen  atom  has  replaced  one  methenyl 
group,  CH,  of  benzene.  The  homologues,  as  Picoline, 
C6H7N;  lutidine,  C7H9N;  collidine,  C8H1TN,  succeed 
each  other  by  the  increment,  CH2,  as  in  the  case  of  the 
benzene  ring,  and  form  a  series  of  nitrite  bases  which  are 
metameric  with  the  amido-bases  of  the  aniline  series. 
About  a  dozen  of  these  bodies  are  known,  but  the  chief 
interest  that  attaches  to  them  results  from  the  theory 
which  supposes  that  they  represent  the  structure  of  some 
of  the  alkaloids,  as  the  amine  and  imine  compounds  do 
the  remainder. 

833.  The   alkaloids    are   very   important    nitrogenous 
compounds,  which  always  exhibit  a  basic  character,  and, 
like  NH3,  unite  directly  with  acids  to  form  crystallizable 
salts,  soluble   in   water.     The   free  alkaloids,   which   are 
precipitated  when  such  solutions  are  neutralized  by  al- 
kalies, or  by  alkaline  bicarbonates,  are  sparingly  soluble 
in  water,  but  dissolve,  with  differences  of  solubility,  in 
alcohol,  amyl  alcohol,  chloroform,  ether,  etc.     Various  re- 
agents produce  insoluble  compounds   when  mixed  with 
the  alkaloids.     Such   are   solutions   of  tannin  and   solu- 
tions of  iodide  of  potassium  containing  I  or  HgI2,  etc. 
Generally    speaking,   the   alkaloid    may   be    regenerated 
from   these   by   soda   lye,  but  sometimes   the   compound 
requires  previous  treatment  with  sulphurous  acid.     It  is 
not  unusual  to  find  several  alkaloids  in  the  same  plant, 
and  their  complete  separation  is  often  a  tedious  labor, 


462  ORGANIC  CHEMISTRY. 

The  alkaloids  and  their  salts  are  characterized  by  a 
bitter  taste,  and  by  their  energetic  action  upon  the  an- 
imal economy.  Very  many  are  important  medicines, 
and  others  are  among  the  most  active  poisons  known. 

834.  Most   alkaloids   are   solids,  and   can    not    be   dis- 
tilled without  decomposition.      Only  three  are  easily  vol- 
atile; viz,  conine,  nicotine,  sparteine. 

Conine,  08II14NII,  obtained  from  the  seeds  of  the  con- 
ium  maculatum,  as  a  pungent,  poisonous  liquid,  of  stupe- 
fying odor;  sp.  gr.,  0.84;  boils,  170°.  It  behaves  as  an 
imide  base,  and  may  be  oxidized  to  normal  butyric  acid. 
It  is  the  noted  "  hemlock  poison  "  of  Socrates. 

Nicotine,  C10II14X2,  is  found  combined  with  malic  acid 
in  tobacco  leaves  (from  0.7  to  7%  ;  Cuba  tobacco  con- 
taining much  less  than  Virginia),  and  may  be  prepared 
by  (1)  soaking  the  leaves  in  dilute  sulphuric  acid,  (2) 
distilling  the  concentrated  extract  with  Kill).  It  is  a 
colorless,  poisonous  liquid,  which  becomes  brown  on  ex- 
posure to  the  air,  having  the  disagreeable  odor  of  rank 
tobacco;  sp.  gr.,  1.02;  boils  at  247°.  When  tobacco  is 
burned,  —  /.  /».,  smoked,  —  it  yields,  besides  the  undecom- 
posed  nicotine,  other  products,  CII4,  C2H6,  etc.,  and  a 
number  of  pyridine  bases,  collidine,  etc.,  scarcely  less 
poisonous  than  itself. 

Sparteine,  (1l5n26X2,  exists  in  the  broom,  spartium 
scoparium,  and  may  be  obtained  from  it  as  a  bitter  nar- 
cotic fluid,  which,  like  nicotine,  is  a  nitrile  base. 

835.  The  other  alkaloids  are  non- volatile.     Opium,  the 
dried  juice   which    has   exuded    from    incisions   made   in 
the  nearly  ripened  seed  capsules  of  the  poppy,  papaver 
somniferum,   is    a   complex    mixture   from    which   sixteen 
different  alkaloids  have  been  obtained,  besides  a  variety 
of  waxes,  etc.,  and  meconic  acid,  C7H4O7,  3II2O.     These 
alkaloids  may  be  obtained  in  colorless  rhombs  and  prisms, 
somewhat  heavier  than  water,  which  are  nearly  all  fusi- 
ble at  between  50°  and  220°.     Their  solutions  are,  with 


OPIUM  ALKALOIDS.  463 

one  or  two  exceptions,  either  optically  inactive  or  laevo- 
rotatory.     The  most  important  are  — 


Morphine,  C17H19NO3. 
Codeine,  C18H21NO3. 
Thebaine,  C19H21NO8. 


Papaverine,  C21H21NO4. 
Narcotine,  C22H23NO7. 
Narceine,  COQHOQNOQ. 


23-l-L29 


When  opium  is  digested  with  warm  water,  most  of  its  alkaloids 
pass  into  solution.  From  such  solutions  the  meconic  and  sulphuric 
acids  present  may  be  removed  by  barium  chloride,  and  ,(2),  on  con- 
centrating the  filtered  liquid,  the  hydrochlorides  of  morphine  and 
codeine  first  crystallize  out,  and  may  be  separated  b}  ammonia  in 
which  only  the  codeine  is  soluble.  (3)  The  mother  liquor  is  mixed 
with  ammonia,  which  precipitates  all  the  others  except  narceine. 
(4)  This  precipitate  is  boiled  with  alcohol  to  dissolve  out  the  the- 
baine,  then  with  potash  to  extract  the  papaverine,  leaving  behind 
the  narcotine. 

Good  Smyrna  opium  contains  about  ten  per  cent  of  morphine, 
but  the  amount  is  variable  —  from  4^  to  24^-.  The  narcotine  is 
generally  less  than  one  fifth  of  this,  and  the  remainder  of  the  al- 
kaloids are  found  in  minute  quantities.  The  peculiar  physiological 
action  of  opium  depends  upon  the  joint  effect  of  all  of  its  active 
constituents.  Nearly  all,  except  papaverine,  are  considered  poison- 
ous. Morphine,  narceine,  and  codeine  are  the  chief  pain-allaying 
and  sleep-producing  constituents.  Thebaine  is  pain-allaying  but 
not  sleep-producing,  and  is  the  most  active  poison  of  the  group; 
and  narcotine  is  reckoned  of  little  value  in  medicine. 

Morphine,  C17H19NO3  -\-  H2O,  crystallizes  in  rhombic 
prisms,  which  are  soluble  in  1000  parts  of  cold  water, 
and  readily  in  solutions  of  the  fixed  alkalies.  The  usual 
salts  are  the  hydrochloride,  C17H19NO3,  HC1 -f- 3H2O, 
and  the  sulphate,  (C17H19NO3)2H2SO4  -f  5H2O,  which 
crystallize  in  slender  needles,  easily  soluble  in  water  and 
in  alcohol.  Morphine  is  readily  oxidized  to  oxy-di-mor- 
phine,  C34H36N2O6,  and  hence  acts  reducing. 

TESTS.  It  reduces  K3FeC3N6,  etc.,  I2O5  (with  separation  of  free 
iodine),  and  produces  a  characteristic  blue  when  mixed  with  neu- 
tral Fe2Cl6. 


464  ORGANIC  CHEMISTRY. 

Codeine,  C18II21XO3 -f-II2O,  is  methyl  morphine,  and 
when  heated  with  IIC1  yields  apomorphinc,  C17I117XO2, 
and  methyl  chloride.  It  resembles  morphine  in  its  ther- 
apeutieal  properties,  but  is  soluble  in  ether  and  in  80 
parts  of  water,  and  does  not  produce  a  blue  coloration 
with  Fe2Cl6. 

Niircotine,  C22II23XO7.  yields  to  Ilf'l,  three  methyl 
groups,  one  after  the  other  becoming  finally  nor-narco- 
tine,  (',  ,,1^  7N(>7,  and  is  further  characterized  by  break- 
ing up  when  boiled  with  water  or  weak  alkalies  into 
mcroninCi  C10II14O4,  an  acid  anhydride  occurring  nat- 
urally in  opium  and  a  variety  of  other  products. 

836.  Piperine,  ri:II19NO3,  constitutes  nearly  nine  per 
cent  of  the   Kast    Indian   peppers.     It  is  almost  tasteless 
because  so  slightly  soluble  in  water;  its  alcoholic  solution 
has  a  sharp,  peppery  taste.     When  this  solution  is  heated 
with  KIIO,  it  forms  pipcric  acid,  C12II10O4,  and  piperi- 
dinc,  CJl^N. 

Piperidiiie  is  an  alkaline  fluid,  smelling  strongly  of 
pepper  and  ammonia,  boiling  at  1(M>°,  and  converted  by 
boiling  with  II2SO4  into  pyridine,  but  it  is  also  formed 
from  pyridine  by  the  action  of  Sn  -f-  HC1. 

837.  Sinapine,  C16II23XO5,  is  found  in  white  mustard 
seeds,  combined  with   CNSII.     On    boiling  ground   mus- 
tard   with    alcohol,  the    sinapine   sulphocyante   dissolves, 
and  may  be  crystallized    in   fine  needles,  which   melt  at 
130°.     The  free  base  is  exceedingly  unstable,  and  is  de- 
composed on   boiling   into  sinapic  acid,   CjjIIjjOg,  and 
neurine,  C5II15XO2  (page  38G). 

838.  The  chinchona  bases  are  the  alkaloids  found  in 
the  bark  of  the  chinchona  trees  of  Peru.     Only  quinine 
and   chinchonine  are  employed  in   medicine,  the   former 
being   held    in    almost  universal   repute   as   a   tonic   and 
febrifuge. 

The   yellow,  or  Calisaya   bark,  contains   the    largest   percentage 


THE  CHINCHONA   GROUP.  465 

(3$.)  of  quinine,  the  grey,  or  Iluanaco,  bark  is  especially  rich  in 
chinchonine  (2$).  The  red  bark  contains  both.  The  alkaloids 
exist  in  these,  as  salts  of  quinic  and  quino-tannic  acid,  and  are 
extracted  (1)  by  treating  the  ground  bark  with  dilute  HC1,  filter- 
ing, and  then  precipitating  the  bases  with  lime.  (2)  This  precip- 
itate is  boiled  with  alcohol,  exactly  neutralized  by  II2SO4,  and 
evaporated.  Quinine  sulphate  first  crystallizes  out,  then  chincho- 
nine sulphate.  The  mother  liquor  retains  the  salts  of  the  other 
bases,  among  which  are  quinidine  and  chinchonidinc,  isomers  of  the 
other  two. 

Quinine,  C20II24N2O2 -f-3H2O,  is  precipitated  from  its 
salts  by  alkalies,  as  a  white  powder,  soluble  in  1670  parts 
of  water,  but  easily  in  ether  and  chloroform.  The  sul- 
phate, (C20II24N2O2)2H2SO4  +  8H2O,  is  the  salt  com- 
monly used  in  medicine,  soluble  in  about  800  parts  of 
water,  but  soluble  in  11  parts  of  water  containing  dilute 
II2SO4,  due  to  the  formation  of  tbe  acid  salt, 

C20II24N2O2,  I12SO4  -f  7II2O  =  quinine  bisulphate. 

All  solutions  containing  quinine  are  characterized  by  a 
bitter  taste,  and  by  a  blue  fluorescence.  They  yield 
when  chlorine  water  is  first  added,  and  then  ammonia, 
an  emerald  green  color. 

Quinidine  resembles  quinine  in  its  medicinal  proper- 
ties, but  is  more  easily  soluble. 

CJiinchonine,  C19H22N2O,  does  not  yield  the  same 
chemical  reactions  with  quinine,  but  has  some  use  as  a 
substitute  for  quinine  in  medicine.  It  is  less  soluble 
than  quinine,  although  its  salts  are  more  soluble  in  water 
and  alcohol.  It  bears  a  close  resemblance  to  its  isomer, 
chinchonidine,  which  occurs  together  with  quinidine  in 
the  last  resinous  mass  obtained  after  the  removal  of  the 
quinine  and  chinchonine  sulphates,  and  sold  as  quin- 
oidine. 

When  the  sulphates  of  these  four  bases  are  heated  to  135°,  two 
other  isomeric  bases  are  produced,  viz,  quinicine  and  chinchonicine. 


466  ORGANIC  CHEMISTRY. 

We    now  have    two   series  of   isomers,  which    are   characterized   hy 
the  deviations  they  severally  produce  in  polarized  light,  viz  : 


C20H24N202. 
Quinine      (left)      —145°. 
Quinicine  (right)  -f-    44°. 
Quinidine  (right)  4-237°. 


C19H22N20. 

Chinchonidine  (left)        -    70.' 

Chinchonicine  (right) -j     46.' 

Chinchonine  (right)  -f  226.' 


All  these,  when  distilled  with  dry  potash,  yield  three 
bases  of  the  formula  CBII2H_nN  ;  as,  chinoline,  C(JII7N, 
which  are  isomerk-  with  a  series,  leucoline,  etc.,  obtained 
from  coal  -tar  naphtha. 

839.  The  strychnos  alkaloids  are  found  in  the  bark 
and  roots  of  the  strychnos  plants,  and  especially  in  the 
needs  or  beans  of  the  *S'.  mix  vomic.a  and  the  8.  »S7.  I<j- 
natii 


They  are  ohtained  (1)  by  boiling  the  crushed  seeds  in  very  di- 
lute II2SO4;  (2)  concentrating  the  liquor,  to  which  a  little  plumbic 
acetate  is  added,  and  (3),  boiling  with  ordinary  alcohol,  and  filter- 
ing hot.  (4)  To  this  is  added  magnesia,  and  the  whole  allowed  to 
stand  for  a  week.  (5)  Finally,  this  precipitate  is  boiled  with  al- 
cohol, which  removes  both  bases.  On  cooling,  the  strychnine  first 
crystallizes  out,  and  then  the  bnicine. 

Strychnine,  C21  II22N2O2,  forms  in  white  rhombic 
prisms,  somewhat  soluble  in  ordinary  alcohol,  y^-,  and 
very  sparingly  in  water.  It  imparts  to  these  solutions 
an  intensely  bitter  taste.  When  taken  in  small  doses, 
-fa  grain,  it  is  a  valuable  tonic,  but  it  is  also  one  of  the 
most  violent  poisons  kno\vn.  Its  effects  are  similar  to 
those  produced  by  tetanus.  It  dissolves  in  cold  II2SO4 
without  change  of  color.  This  solution,  oxidized  with 
K2Cr2O7,  PbO2,  etc.,  gives  characteristic  colors;  first,  a 
bluish  violet,  then  a  red,  and  finally  green. 

Strychnine  is  entirely  removed  from  its  solutions  by 
animal  charcoal. 

Brucine,  C22H26N2O4  -f  41I2O.  resembles  strychnine 
in  its  physiological  properties,  but  it  is  decidedly  less 


THE  ATROPINE  ALKALOIDS.  467 

poisonous.  It  is  sparingly  soluble  in  cold  water,  but 
easily  in  alcohol.  Strong  nitric  acid  colors  brucine  to  a 
fine  and  characteristic  red  color,  which  becomes,  on 
warming,  yellow,  which  is  changed  to  a  deep  violet  by 
reducing  agents,  like  SnCl2. 

Citrarine,  C18H35N,  is  the  active  principle  in  the  South 
American  arrow  poison,  which  is  probably  the  dried  juice 
of  some  strychnos-like  plant. 

TJie  Ptomaines  are  a  group  of  alkaloids,  some  of  which 
are  volatile  and  not  poisonous,  while  otters  resemble 
strychnine  both  in  their  chemical  reactions  and  in  their 
poisonous  properties.  They  are  obtained  from  albumin- 
oid substances,  which  have  decomposed  without  free  ac- 
cess to  the  air  (canned  meats?  mouldy  maize?),  and 
hence  are  found  in  buried  animal  remains,  and  are  said 
also  to  occur  in  fresh  blood  and  egg  albumin. 

Eserine,  or  physostigmine,  C15H21N"3O2,  is  the  resin- 
ous extract  of  calabar  beans,  easily  melted  and  quite  sol- 
uble in  alcohol  and  cold  water.  It  is  readily  oxidized, 
and  is  one  of  the  most  active  poisons  known.  It  pro- 
duces a  marked  contraction  in  the  pupil  of  the  eye. 

840.  The  atropine  group  contains  several  alkaloids  of 
the  formula,  C17II23NO3,  which  strikingly  resemble  each 
other.  When  boiled  with  strong  KHO  or  HC1,  they 
are  converted  to  tropic  acid,  C9H10O3,  and  C8H15NO, 
tropine,  or  its  isomer.  Conversely,  the  mixture  of  these 
substances,  when  boiled  for  some  hours  with  dilute  HC1, 
produces  atropine. 

(1)  Atropine  is  identical  with  daturine,  and  is  obtained 
from  the  atropa  belladonna  (deadly  nightshade)  or  from 
the  datura  stramonium  (thorn  apple)  by  warming  the 
seeds  of  these  plants  with  dilute  potash,  and  then  shak- 
ing the  mixture  with  chloroform.  On  evaporating  this, 
redissolving  in  alcohol,  and  then  diluting  with  water,  the 
atropine  separates  in  oily  drops,  which  change  to  bright 
needles  slightly  soluble  in  water,  and  melting  at  114°. 


468  ORGANIC  CHEMISTRY. 

(2)  The  mother  liquor  above  obtained,  contains  hyoscy- 
amine,  which  is  preferably  prepared  from  hyoscyamus 
niger  (henbane),  which  also  contains  a  third  isomer, 
hyoscine.  The  hyoscyamine  forms  in  silky  needles,  easier 
soluble  than  those  of  atropine,  and  of  a  lower  melting 
point,  108°. 

All  these  are  active  poisons,  and  are  characterized  by 
strongly  dilating  the  pupil  of  the  eye. 

841.  Various  other  plants  contain  alkaloids  peculiar  to 
them.  Among  these  are: 

Pilocarpine,  Clllllf^2O2J  is  a  poisonous  base  resembling  nico- 
tine. When  heated  by  itself,  or  with  IR'l,  it  is  changed  to  jabo- 
rinc,  a  very  strong  base,  which  is  also  found  in  Juborandi  leaves. 
It  is  also  poisonous,  acting  like  atropine. 

Solan i lie,  C42H75N()15,  i.s  a  poisonous  glucoside  found  in  all  the 
Bolanum  plants,  and  readily  obtained  from  the  fresh  buds  of  po- 
tatoes which  have  sprouted  in  the  dark.  It  is  resolved  on  boiling 
with  dilute  IK'l  into  glucose  and  solanidine,  C26H41NO2.  This  al- 
kaloid crystallizes  in  fine  long  needles,  which  melt  at  200°,  and 
may  be  in  part  sublimed.  It  is  colored  red  by  II2SO4. 

The  mat  rum  family  of  plants  contain  no  U-ss  than  seven  alkaloids. 
The  only  important  ones  are  ceradine,  C'12II49NO9,  until  recently 
known  as  veratrinr  (which  name  is  now  given  to  C37II53NO1  j ),  and 
jervine,  C26II43NO2.  The  first  of  these  is  characterized  by  produc- 
ing, when  taken  into  the  nose,  a  most  violent  sneezing;  when  swal- 
lowed, it  is  a  powerful  emetic,  and  also  a  narcotic  poison.  Both 
it  and  the  veratrine  dissolve  in  H2SO4,  with  first  a  yellow  and 
then  a  carmine-red  coloration.  Jervine  so  treated  becomes  finally 
emerald  green. 

Aconitine,  C33H43NO,2,  is  obtained  from  the  roots  of  the  acon- 
ilum  napettus  (monk's  hood)  in  rhombic  tables,  melting  at  183°,  and 
sparingly  soluble  in  water.  It  has  a  peculiar  prickling  taste,  and 
is  exceedingly  poisonous. 

Colchicine,  C17II19NO5,  is  a  yellow  amorphous  powder  obtained 
from  the  meadow  saffron,  easily  soluble  in  water,  and  melting  at 
140°.  It  has  an  intensely  bitter  taste,  and  is  an  active  poison. 

Emetine,  C28H40N2O5,  is  the  active  principle  of  the  ipecacuanha 
root.  It  is  a  medicine,  valuable  in  small  doses  for  bronchial  troub- 
les, but  in  larger,  acts  as  a  violent  emetic,  and  is  poisonous. 


RECAPITULATION.  469 


Recapitulation. 

Among  the  aromatic  compounds,  which  contain  nitrogen,  are: 

I.  The  following   classes  of  bases  < 

as  from  benzene,       .         .         .         .  C6H6. 

(1)  Amine,  C6H5NH2. 

(2)  Hydrazo,  .         .         .        .        .  (C6H5)2(HN)2. 

(3)  Azo,  .  (C6H5)2N2. 

(4)  Azoxy,  .  (C6H5)2  •  N2  •  O. 

(5)  Diazo, C6H5  •  N2  •  Cl. 

(6)  Hydrazin, C6H5(NH)2H. 

(7)  Nitrile, C6H5CN. 

These   include   a  great  variety   of   dye-stuffs,  —  aniline,  rosan- 
iline,  naphthylamine,  etc. 

II.  Products  of  destructive  distillation,  like  the  pyridine  bases, 
CnH2n-5,  and  chinoline,  CnH2,4_n.* 

III.  The  vegetable  alkaloids.     Some  of  these  resemble  the  amine 
bases,  some  the  pyridine,  in  their  chemical  structure. 

IV.  The  glucosides  which  contain  these  alkaloids,  as  indicah. 

V.  Other  organic  compounds  containing  nitrogen  are  the  amides 
and  amic  acids  (Chapter  XXIV);  and, 

VI.  The  nitro  (NO2)  and  nitroso  (NO),  formed  by  substituting 
these  radicals  for  hydrogen. 

*  Another  series,  CnH2n-3N,   is  represented  by  pyrrol,  C4HBN,  which  is 
also  found  in  coal-tar. 


CHAPTER   XXIX. 

VEGETABLE    AXD    ANIMAL    CHEMISTRY. 

842.  The  molecular  structure  of  most  of  the  substances 
immediately   connected    in    the   chemical   changes  which 
take    place    in    living   plants   and    animals    is   practically 
unknown.     A    portion    of   these,  —  the    starches,    sugars, 
amides,  etc.,  —  have  been  assigned  to  a  provisional  place 
in  the  chemical    system,  hut   there   remain  others  which 
chemists  have  failed  to  classify.     Among  the  most  impoi1- 
tant  of  these  are  those  brought  together  in  this  chapter. 

843.  The  drugs  used  in  medicine  contain  a  number  of 
active    constituents    which    have    not    been    satisfactorily 
grouped  from  the  chemist's  point  of  view.     Among  these 
are  the  so-called  l*  bitter  principles"  which  have  a  bitter 
taste,  and  are  popularly  regarded  as  tonics;  such  as  the 
bitter  of  hops,  C16H26O4,  of  quassia  wood,  C10H12O3, 
and  of  columbo-root,  C21H22O7. 

Aloin,  C17II18O7,  the  purgative  principle  of  Barbadoes 
aloes,  has  a  taste  at  first  sweetish,  and  then  intensely 
bitter.  By  prolonged  action  of  HNO3  it  is  converted  to 
chrysammic  acid,  C14II4(NO2)4O4,  which  is  used  as  a 
dye. 

Santonin,  C15H10O3,  and  absinthiin,  C20H28O4,  found 
in  certain  species  of  wormwood,  and  koussin,  C31H38O10, 
from  the  kousso  plant,  are  yellowish  substances  of  very 
bitter  taste,  classed  in  medicine  as  anthelmintics. 

Picrotoxin,  C15H16O6 -|- H2O,  is  the  poison  of  the  coc- 
culus  indicus,  intensely  bitter, and  a  good  reducing  agent. 

With  these  substances  may  be  classed  lactucin,  a  bitter 
substance  found  in  lactuceriu,  C20H32O2,  the  dried  sap 

(470) 


THE  BILE.  471 

of  the   lettuce,  supposed   to   possess  narcotic   powers  re- 
sembling that  of  opium. 

Some  glucosides  are  popularity  named  with  these  because  of  their 
bitter  taste,  as  chiretin,  salicin,  phlorizin,  and  arbutin,  but  are  not 
otherwise  related.  A  few  glucosides  yield,  besides  glucose,  a  crys- 
tallizable  body  which  might  be  reckoned  with  this  group,  as  cescu- 
lin,  C15H16O9,  found  in  the  horse-chestnut  bark,  which  yields 
cescuktin,  C9H6O4.  Another  is  quwcetrin,  C36H38O2,  which  contains 
quercetin,  C24Hi6Ou,  a  yellow  crystallizable  substance. 

On  the  other  hand,  a  number  of  substances  put  into  this  group 
have  neither  taste  nor  odor.  Such,  for  example,  is  C10IIi0O3,  cu- 
bebin,  from  the  piper  cubeba;  caryophyllin,  C2oH32O2,  from  cloves, 
and  gentisin,  C14H10O5,  from  gentian  roots.  And  with  them  a 
group  of  bodies  which  are  spoken  of  as  indifferent  matters,  in  the 
sense  that  they  are  neither  bases  nor  acids,  as  C24H30O7,  atha- 
mantin,  from  the  alhamanta  oreoselinum. 

Carotin,  C18H24O,  the  coloring  matter  of  the  carrot,  from  which 
it  may  be  obtained  in  red-brown  cubes,  of  pleasant  violet-like  odor. 

Cantharidin,  C10H12O4,  is  obtained  from  Spanish  flies,  potato- 
bugs,  and  other  beetles,  in  rhombic  tables  which  are  insoluble  in 
water.  It  is  an  active  blistering  agent  and  poison. 


THE  BILE. 

844.  The  bile  of  animals  is  the  secretion  of  the  liver, 
which  collects  in  the  gall-bladder.  It  is  a  mixture  con- 
taining in  solution  a  variety  of  substances,  among  which 
are  fatty  soaps,  lecithins  (p.  407),  cholesterin  (p.  433), 
certain  pigments,  and  the  sodium  salts  of  the  bile  acids 
(§729). 

The  acids  found  in  the  bile  of  oxen  are  glycocholic  and 
taurocholic,  both  of  which  yield,  on  boiling  with  dilute 
alkalies,  the  same  decomposition  product;  viz,  cholic  acid, 
C24H4005+H20. 

This  acid  may  be  obtained  in  quadratic  octahedrons,  soluble  in 
alcohol,  and  is  decomposed,  upon  boiling  with  HC1,  with  formation 
of  dyslysin,  C24H36O3  and  2H2O.  These  substances,  when  gently 
warmed  with  strong  sulphuric  acid  and  a  little  sugar,  give  a  beautiful 


472  ORGANIC  CHEMISTRY. 

violet  red  coloration,  which  is  known  as  Pettenkofer's  test"  (§729). 
The  acids  are  prepared  (1)  by  treating  fresh  ox -gall  for  several 
days  with  HC'l  and  ether;  (2)  then  dissolving  the  resinous  mass, 
which  has  formed,  in  boiling  water,  and  (3),  crystallizing. 

Glycocholic  acid  separates  out  first  in  fine  white  nee- 
dles, soluble  in  about  100  parts  of  cold  water.  The 
mother  liquor  contains  taurocholic  acid,  also  obtainable 
in  silky  needles.  Both  these  acids  have  a  sweetish-bit- 
ter taste,  and  give  a  loamy  lather  when  shaken  up  with 
water.  The  second  product  of  the  decomposition  of  gly- 
cocholic  acid  is  glycocoll  (p.  384),  or  ylycocine, 

C26II43N06  +  II20  -  C24II400.  +  NII2    CII2    COOH, 

and  the  second  product  of  taurocholic  acid  is  taurine 
(p.  386), 

C26H46^SO7  +  II20=C241I40O5  +  NH2   C2II4   SO2OH. 

CJlycocine  and  taurine  are  present  in  the  bile  of  most 
animals,  not  free,  but  in  combination  with  cholic  or  a 
similar  acid,  and,  together,  forming  sodium  salts.  Ox-bile 
contains  rather  more  of  glyco-cholic  than  of  tauro-cholic 
acid.  Pigs  bile  contains  C27II43NO5,  hyo-ylycocholic 
acid,  with  a  little  hyo-taurocholic  acid.  The  acid  of  goose- 
bile  is  principally  cheno-taurocholic  acid,  C20II49NS()6. 

The  color  of  the  bile  varies  from  a  golden-yellow  in  man,  the 
greenish-brown  of  herbivora,  to  the  bright-green  of  birds,  and  is 
due  mainly  to  a  reddish-brown  pigment,  bilirubin,  Ci2H36N4O6, 
and  a  green  pigment,  biliverdin,  C32H36N4O8.  The  first  dissolves 
in  alkaline  liquids,  with  an  orange-red  color,  which  appears  yellow 
when  much  diluted,  as  noticed  in  jaundice.  This  solution  readily 
absorbs  oxygen,  and  becomes  green  from  the  formation  of  biliverdin. 

Gmelin's  test  is  founded  upon  this  property,  and  is  made  by 
adding  to  bile,  sodium  nitrate,  and  then  pouring  over  this  strong 
II2SO4.  The  nitrous  acid  which  is  evolved  colors  it  first  green, 
then  blue,  violet,  red,  and  at  last  a  yellow. 

Certain  intestinal  concretions,  found  in  Persian  goats,  and  known 
as  "Oriental  Bezoar  Stones,"  contain  lithqfellic  cci'e/,  C.'20H3GO4,  which 
gives  Pettenkofer's  test,  and  in  other  respects  resembles  glycocholic 
acid. 


PROTEIN  SUBSTANCES.  473 


PROTEIN  SUBSTANCES. 

845.  The  protein  or  albuminoid  substances  are  formed 
primarily  in   plants,  and  are  stored   up  in  plant  tissues 
and   organs,   but    especially   in    leaf  buds   and   in   seeds. 
The  animals  which  feed  upon  these  so  change  their  ex- 
ternal form,  and  assimilate  them,  that  they  become  the 
essential  constituents  of  the   nutritive  fluids  of  animals, 
and   most   of  the    soft   solids    of  their   organism,  —  flesh, 
tendons,  etc.     Nevertheless,  the   composition  and   chem- 
ical properties  of  these  compounds  are  very  much  alike, 
whether  derived   from  plants  or  from  animals.     In  the 
living  organism,  they  are  found  mixed  with  various  other 
bodies   (water,  chlorides,   phosphates,   fats,  etc.),  so  that 
it  is  an  exceedingly  difficult  matter  to  obtain  them  suf- 
ficiently pure  for  accurate  determination  of  their  compo- 
sition, or  to  obtain  satisfactory  formulae  for  any  of  them. 
The  results  of  analyses  show  an  average  percentage  of 
C  53,  H  7,  N  15.8,  S  1.4  (O  22.8  by  difference),  which 
corresponds  to  C72H118N18SO22. 

It  is  possible  that  the  differences  in  their  properties  are  due  to 
the  presence  of  isomers  or  polymers  of  some  protoplasmic  substance 
as  yet  undiscovered.  It  is  very  evident  that  they  must  have  a  high 
molecular  weight:  (1)  because  they  do  not  diffuse  through  mem- 
branes; (2)  they  are  exceedingly  prone  to  decomposition;  and  (3), 
yield  an  unusual  number  of  decomposition  products.  Among  these 
are  gases,  like  CO2,  H2S,  and  NH3;  amide  bodies,  such  as  glyco- 
cine,  leucine,  tyrosine,  aspartic  acid,  and  glutamic  acid ;  the  fatty 
acids  and  their  aldehydes  from  formic  to  palmitic;  also,  oleic, 
lactic,  and  succinic  acids;  besides  various  aromatic  compounds,  as 
benzoic  acid,  phenol,  indol,  and  skatol. 

846.  The  albumins,   soluble    in  water,  are  three:    (1) 
Albumin,  which   is   coagulated   or  rendered   insoluble   at 
the  temperature  of  72°;    (2)   Casein,  which   is  only  par- 
tially coagulated  upon   boiling,  but  completely  upon  the 
addition   of  acetic   acid;   (3)  and   the   albumin  of  blood 


474  ORGANIC  CHEMISTRY. 

plasma,  which  separates,  as  the  insoluble  fibrin  upon  ex- 
posure to  the  air.  When  once  coagulated,  these  strongly 
resemble  the  insoluble  albumins,  globulin,  lardacein,  and 
the  derived  albumins. 

847.  All  the  albuminoids  are  soluble  in  dilute  mineral 
acids,  and  in  dilute  solutions  of  the  alkalies,  and  of  cer- 
tain salts,  like   NaCl.     (1)  They  are  precipitated  there- 
from by  stronger  acids  and  salt  solutions,  and   by  anti- 
septics, like  the  salts  of  llg  and  Cu,  by  tannin,  carbolic 
acid   and   alcohol,   in   white   flocks   (coagulated   albumin), 
which,  when  dried,  form  a  horny,  semi-transparent,  amor- 
phous mass.     (2)   Heated  by  themselves  in  the  air,  they 
carbonize   and   emit   an   odor  resembling   that  of  burnt 
feathers.      (3)    Heated    with    moderately   strong    IINO3, 
they  change  to  xanthoproteic  acid,  an  orange -yellow  sub- 
stance,   which  dissolves  in   alkalies   with   an   orange- red 
color.     (4)  Heated  with   Millon's  re-agent,*  mercuric  ni- 
trate, they  yield  a  fine  red  color. 

848.  The  albumins,  properly  so-called,  are  found  in  the 
white  of  eggs,  in  the  serum  of  blood,  and  in  the  juices  of 
most  vegetables.     Both  egg  and  blood  albumin  have  an 
extensive   use  in  calico  printing,  and  in  the  preparation 
of  albuminized  paper  for  the  use  of  photographers. 

The  globulins  are  soluble  in  dilute  solutions  of  sodium 
chloride,  but  not  in  pure  water.  The  animal  globulins 
comprise:  (1)  Vitellin,  which  is  a  constituent  of  the  yolk 
of  hen's  eggs ;  bodies  similar  to  this  are  found  in  the 
chyle  and  in  the  crystalline  lens.  (2)  Myosin,  or  flesh 
fibrin,  which  is  found  in  the  living  muscle  as  a  liquid; 
after  death  (in  rigor  mortis}  it  curdles  rather  than  coag- 
ulates, since  it  may  be  readily  extracted  from  finely- 
divided  flesh  by  means  of  a  dilute  solution  of  NII4C1. 

(3)   The  blood  and   all  the  serous  liquids  of  the  body 

<•  Prepared  by  digesting  1  part  of  Hg  with  1  part  HNO3.  and  then  adding 
4HaO.  The  clear  liquid  which  separates  from  the  insoluble  portion  is  the 
re  agent. 


PROTEIN  SUBSTANCES.  475 

contain,  not  only  serum-albumin,  but  also  two  modifica- 
tions of  globulin.  These  are  known  as  the  fibrino -plastic 
substance  and  fibrinogen.  When  the  blood  has  been  re- 
moved from  a  living  animal,  these  two  substances  unite 
and  form  fibrin,  which  is  the  chief  part  of  the  blood-clot. 
This  fibrin  may  be  obtained  as  a  white,  stringy  solid  by 
beating  freshly-drawn  blood  with  twigs,  and  then  wash- 
ing with  water.  Fresh  fibrin  resembles  dried  albumin, 
but  is  more  readily  oxidized,  decomposing  hydric  per- 
oxide with  evolution  of  oxygen,  and  is  quickly  dissolved 
by  the  gastric  juice. 

(4)  The  plant  globulins  are  very  similar  to  those  of 
animals.  Maize  and  peas  contain  both  vitellin  and  my- 
osin.  Squash-seeds  contain  a  large  amount  of  the  former, 
and  white  mustard-seeds  are  especially  rich  in  the  latter. 

The  gluten  found  in  the  cereals,  and  which  may  be 
obtained  from  wheat  flour  by  kneading  it  with  water 
until  all  the  starch  has  been  washed  out,  is  a  tough 
elastic  substance  of  the  utmost  importance  in  bread- 
making.  It  is  frequently  called  vegetable  fibrin,  but  is 
really  a  mixture  containing  gluten -fibrin,  mucedin,  and 
gliadin,  or  vegetable  gelatin,  which  are  fibrin-like  bodies 
that  may  be  extracted  from  crude  gluten  by  strong  al- 
cohol, leaving  behind  a  fourth  albuminoid,  which  is 
gluten-casein. 

The  animal  caseins  are  found  dissolved  in  milk  by 
reason  of  the  presence  of  an  alkali,  and  hence  they  are 
spoken  of  as  alkali  albuminates.  When  this  alkali  is 
neutralized  by  an  acid,  as  the  lactic  acid  of  sour  milk, 
the  casein  separates  out  as  a  curd.  The  same  change 
is  effected  by  means  of  the  ferment  in  calf-rennet,  which 
is  used  in  the  manufacture  of  cheese.*  It  is  probable 
that  casein  is  a  mixture  of  several  albuminoids,  inas- 
much as  the  casein  of  cow's  milk  differs  in  some  respects 
from  that  of  other  mammalia.  An  " artificial  casein" 

*One  part  of  this  ferment,  "tab,"  suffices  for  800,000  parts  of  casein. 


476  ORGANIC  CHEMISTRY. 

may  be  derived  from  egg  or  serum  albumin  by  the 
prolonged  digestion  of  either  in  caustic  soda,  and  subse- 
quent precipitation  by  acetic  acid.  This  is  not  coagula- 
ble  by  rennet. 

The  vegetable  caseins  are  alkali-albumins,  which  exist 
in  peas  and  beans  as  leyumin ;  in  lupines  and  the  kernels 
of  stone  fruits,  as  conylutin ;  and  in  the  cereals,  as  ytuten- 
casein. 

All  these  forms  of  casein,  when  freshly  precipitated 
and  thoroughly  washed,  are  insoluble  in  pure  water,  but 
are  readily  soluble  in  dilute  alkalies,  and  reprecipitated 
therefrom  by  very  dilute  acids,  as  a  snow-white  powder, 
entirely  free  from  •'  ash,"  of  a  decidedly  acid  reaction, 
and  soluble  in  hot  alcohol. 

Cheese  is  the  "ripened  curd"  of  milk,  containing  more 
or  less  of  the  milk  fats  and  salts.  The  ripening  of  cheese 
is  due  to  a  fermentation  by  which  a  portion  of  the  albu- 
minoid is  decomposed  with  formation  of  certain  products 
which  give  to  old  cheese  its  peculiar  odor  and  taste. 

The  Chinese  make  a  cheese  from  the  pulp  of  ground 
peas,  which  is  said  to  resemble  very  closely  that  pro- 
duced from  milk. 

849.  Albumin  derivatives  are  formed  (1)  by  the  action 
of  dilute  alkalies  upon  the  albuminoids,  as  already  men- 
tioned in  artificial  casein ;  (2)  by  dissolving  any  of  those 
described  in  dilute  acids,  thereby  forming  acid  albumins, 
or  syntonins.  On  neutralizing  the  acid,  these  bodies  are 
thrown  down  as  flocculent,  gelatinous  bodies,  insoluble  in 
hot  alcohol,  but  easily  dissolved  in  alkalies,  as  alkali- 
albumins,  and  as  easily  reconverted  to  acid-albumins  by 
acids. 

(3)  Coagulated  albumin  is  also  considered  as  a  de- 
rived albumin.  When  obtained  from  albumin,  globulin, 
fibrin,  etc.,  by  heating  or  by  alcohol,  it  becomes  diffi- 
cultly soluble  in  dilute  alkalies  and  acids,  although  sol- 
uble by  prolonged  digestion  with  acetic  acid.  It  may 


PROTEIN  SUBSTANCES.  477 

be  converted  into  alkali -albumins  by  caustic  soda,  or 
into  acid  albumins  by  strong  hydrochloric  acid. 

(4)  The  peptones  are  the  products  obtained  by  the  di- 
gestion of  the  food  albuminoids  with  the  gastric  and 
pancreatic  juices.  They  are  naturally  mixtures  of  sev- 
eral decomposition  products.  Such  of  these  as  resemble 
albumin  in  percentage  composition  differ  essentially  in 
several  important  particulars.  They  are  soluble  in  water, 
and  are  easily  diffusible.  Their  aqueous  solutions  are 
not  precipitated  by  heating  with  dilute  acids,  alkalies, 
nor  by  alkaline  salts,  but  are  coagulated  by  strong  al- 
cohol and  by  HgCl2. 

They  are,  therefore,  the  modified  forms  by  means  of 
which  the  various  albuminoid  substances  enter  into  the 
nutritive  fluids  of  the  animal  organism,  and  of  course 
must  exhibit  differences  due  to  the  character  of  the  food 
and  the  process  by  which  the  peptone  is  obtained  for 
examination. 

850.  The  soluble  nitrogenous  ferments  have  about  the 
same  percentage  composition  as  the  albuminoids.  They 
are  soluble  in  water,  and  are  not  precipitated  upon  boil- 
ing, although  they  lose  their  peculiar  fermentative  power 
thereby.  No  formula  can  be  given  for  any  one  of  them. 
The  vegetable  ferments  are  emulsin  in  the  juice  of  al- 
monds, myrosin  in  mustard  seeds,  and  diastase,  which  is 
the  ferment  formed  from  gluten  in  the  germination  of 
seeds,  and  is  an  agent  by  which  starch  is  changed  to 
dextrin,  and  then  to  malt  sugar.  The  animal  ferments, 
ptyalin  of  the  saliva,  and  trypsin  of  the  pancreatic  juice, 
have  the  same  power  when  in  alkaline  solution. 

The  pepsin,  which  is  the  active  ferment  of  the  gastric 
juice  of  the  stomach,  converts  all  of  the  albuminoids 
into  syntonins,  and  then  into  soluble  peptones,  etc.  It 
acts  most  readily  at  30°-40°,  and  is  hindred  by  the 
presence  of  strong  alcohol  and  the  caustic  alkalies.  The 
pepsin  sold  by  apothecaries  is  obtained  by  scraping  the 


478  ORGANIC  CHEMISTRY. 

mucous    membrane  of  a   pig's  stomach,  and    afterwards 
drying  the  pulp  so  obtained. 

With  these  ferments  must  undoubtedly  he  mentioned  the  poisons 
present  in  the  venom  of  snakes,  of  rahies,  and  of  glanders,  and 
perhaps,  also,  other  products  of  derived  albumins. 

The  yeast- plant,  the  various  forms  of  bacteria,  and  other  bodies 
supposed  to  act  as  "disease  germs,"  are  organized  plants  or  animals. 
They  contain  nitrogen,  and  require  nitrogenous  food  for  their  sup- 
port. They  are  known  to  multiply  with  marvellous  rapidity,  and 
to  be  destroyed  by  agents  that  coagulate  albumin. 

851.  The  haemoglobins  are  the  blood  pigments  of  ver- 
tebrate animals,  and  may  be  obtained  from  the  red  cor- 
puscles of  arterial  blood  in  fine  rhombic  crystals.  These 
crystals  arc  oxy-hcemoglobin  :  that  is,  they  are  hemoglo- 
bin combined  with  oxygen,  but  this  union  is  so  feeble 
that  the  oxygen  is  given  off  when  the  warmed  blood  is 
brought  into  a  Torricellian  vacuum,  and  is  re-absorbed 
on  exposure  to  the  air.  Reducing  agents,  like  ferrous 
salts,  also  convert  oxy-hffimoglobin  to  haemoglobin.  This 
is  very  soluble  in  water,  and  greedily  absorbs  oxygen, 
becoming  reconverted  to  oxy-ha?moglobin. 

This  substance  is  the  carrier  of  oxygen  to  the  body. 
The  red  or  arterial  blood,  during  its  circulation,  parts 
with  its  oxygen,  and  takes,  in  its  place,  the  carbonic 
anhydride,  which  is  a  waste  product  of  the  tissues,  and 
becomes  the  purple  or  venous  blood.  As  this  passes 
through  the  lungs,  the  reverse  action  takes  place,  car- 
bonic anhydride  is  given  off,  and  oxygen  absorbed. 

Certain  gases,  like  carbonous  oxide,  form  more  stable  compounds 
with  the  haemoglobin,  and  prevent  the  absorption  of  oxygen,  and, 
therefore,  act  as  powerful  poisons. 

The  composition  of  haemoglobin  must  be  exceeding  complicated. 
The  formula,  C6ooH96oOi  79N154FeS3,  has  been  proposed  for  it, 
which  supposes  a  molecular  weight  of  13332,  or  nearly  7000  times 
that  of  hydrogen.  It  contains  0.42  per  cent  of  iron.  The  amount 
of  luvmoglobins  in  blood  varies  from  12.17<&  in  women,  to  13.45^, 
in  men. 


GELATINS.  479 

Haematm,  C35H34FeN4O5,  is  obtained  by  treating  defibrinated 
blood  witb  acetic  acid.  There  first  forms,  huematin  acetate,  which  may 
be  obtained  in  microscopic  crystals,  which  are  sometimes  regarded  as 
test  for  blood  in  medico-legal  cases.  On  neutralizing  this  acid  so- 
lution with  an  alkali,  the  hajmatin  falls  in  brownish  flocks,  which, 
on  drying,  becomes  a  bluish-black  powder.  It  is  a  moderately 
stable  substance,  which,  when  heated  strongly,  leaves  behind  a 
residue  of  ferric  oxide  (7$>). 

The  animal  mucus,  which  is  found  in  the  glairy  exudations  of  the 
mucous  membranes,  and  in  many  secretions,  bile,  synovial  liquor, 
saliva,  etc.,  yields  syntonin  upon  boiling  with  dilute  mineral  acids. 
The  chief  constituent  of  these  substances  is  mucin,  which  is  easiest 
obtained  from  edible  snails.  It  is  easily  soluble  in  dilute  alkalies, 
and  precipitated  from  such  solutions  by  alcohol,  or  by  acetic  acid. 

Para-albumin,  and  the  so-called  amyloid  matter  or  lardacein,  are 
modified  albumins  produced  in  certain  diseases. 

852.  The  gelatins  do  not  exist  ready  formed  in  the 
animal,  but  are  manufactured  from  two  varieties  of  pro- 
tein substances,  named  collagen  and  chondrogen. 

Collagen  is  found  in  the  connective  tissues, —  skin,  ten- 
dons, etc.,  —  and  in  that  portion  of  the  bone  (osseiri) 
which  is  not  dissolved  by  dilute  HC1.  The  dried  air- 
bladder  of  the  sturgeon  (isinglass)  is  a  variety  of  it.  The 
formula,  C102H149N31O38,  represents  very  nearly  the 
average  composition  of  ossein. 

Cliondrogen  is  found  in  permanent  cartilage,  in  the  cor- 
nea of  the  eye,  and  in  young  bones  previous  to  their 
hardening.  It  is  probably  a  mixture  containing  mucin 
and  a  variety  of  collagen ;  but  the  glue  (chondrin)  that 
is  made  from  it  differs  from  ordinary  glue  made  by  boil- 
ing collagen,  in  some  important  particulars,  having  less 
adhesive  power,  and  yielding  little  or  no  glycocoll  upon 
decomposition. 

Nevertheless,  these  substances  agree  in  most  of  their 
properties.  They  putrefy  readily  when  in  the  moist 
state,  and  yield  leucine  and  other  common  products  of 
decomposition.  The  putrefaction  of  collagen  is  prevented 
by  tannin,  as  is  splendidly  exemplified  in  the  conversion 


480  ORGANIC  CHEMISTRY. 

of  raw  hides  into  leather.  They  are  both  quite  insoluble 
in  cold  water,  but  dissolve  in  boiling  water.  This  solution, 
upon  cooling,  sets  into  a  soft  jelly-like  mass  which  is,  when 
dried,  the  gelatin  of  commerce.  The  gelatin  used  for  jel- 
lies, soups,  etc.,  is  made  from  selected  materials  with,  per- 
haps, the  addition  of  rock-candy.  Printers'  ink-rolls  are 
mixtures  of  glue  and  molasses.  The  gelatin  capsules  of 
the  apothecaries  are  made  from  gelatin,  gum  arabic, 
sugar,  and  glycerol.  The  addition  of  the  two  latter  sub- 
stances impart  a  great  degree  of  flexibility  to  the  gelatin. 

853.  The  best  glue  is  made  from  cuttings  of  hides,  etc., 
and  is  dried  at  25°  in  shallow  trays,  and  finally  upon 
wire  netting.  It  is  an  amorphous,  translucent  substance 
of  a  light  amber  color,  valuable  because  of  its  adhesive 
power  when  applied  to  wooden  joinings.  Placed  in  cold 
water,  it  does  not  dissolve,  but  swells  up  to  three  or  four 
times  its  former  volume.  On  warming  this  swollen  mass 
it  dissolves,  but  again  gelatinizes  upon  cooling.  Long 
boiling  of  glue  destroys  its  valuable  adhesive  properties. 
The  gelatinizing  of  glue  may  be  prevented  by  the  addi- 
tion of  acetic,  or  a  very  little  nitric,  acid  to  its  aqueous 
solution,  without  perceptible  loss  of  its  adhesive  proper- 
ties (liquid  glue). 

When  a  solution  of  glue  is  mixed  with  potassium  bi- 
chromate, and  exposed  to  sunlight,  it  forms  a  solid  mass 
insoluble  in  water.  This  property  is  applied  in  photo- 
graphic printing.  Gelatin  plates,  containing  K2Cr2O7, 
are  exposed  to  light  beneath  pictures  upon  glass,  and 
are  then  washed  in  water.  The  shaded  portions  soften 
and  are  easily  removed,  and  leave  behind  a  raised  sur- 
face, which  represents  the  lights.  The  plate  so  prepared 
is  smeared  with  printers'  ink,  and  impressions  taken,  as 
in  lithography. 

The  plates  used  in  instantaneous  photography  are  gelatin  "bro- 
mized"  by  long  boiling  with  a  solution  of  ammonium  bromide,  and 
subsequent  treatment  with  silver  nitrate. 


RECAPITULATION.  481 

Efastin  is  found,  along  with  collagen,  in  all  the  elastic  tissues, 
as  in  the  arteries.  It  resembles  albumin  in  its  decomposition 
products. 

Keratin  forms  the  chief  part  of  the  epidermis,  —  nails,  hoofs, 
horns,  hair,  wool,  feathers,  etc.  It  gives  Millon's  reaction,  and  dis- 
solves in  water  heated  to  200°,  but  it  does  not  gelatinize  upon 
cooling. 

The  two  substances  next  described  contain  no  sulphur,  although 
in  most  other  respects  they  resemble  the  other  protein  compounds. 

Sericin  (C15H25N5O8?),  is  obtained  in  solution  when  raw  silk  is 
boiled  for  some  hours  in  water.  It  possesses  the  power  of  gelatin- 
izing when  present  in  so  small  an  amount  as  one  per  cent.  It  is 
silk -gelatin.  The  portion  of  silk  insoluble  in  water  is  fibroin 
(e,5H23N5O6?).  It  constitutes  f  of  the  silk,  and  is  the  silk-albu- 
minoid. 

Nude'in  is  found  in  the  blood  corpuscles  of  snakes,  and  is  the 
basis  of  pus  globules.  It  does  not  give  the  protein  reactions,  and 
is  characterized  by  its  resistance  to  the  digestive  ferments,  dilute 
acids,  and  alkalies.  It  contains  a  notable  amount  of  phosphorus, 
and  may  be  regarded  as  a  tetrabasic  acid  having  the  formula, 
C29H49N9P3O22. 

Cerebrin,  C57H110N2-O25,  also  occurs  in  pus  corpuscles,  but  much 
more  abundantly  in  brain  and  nerve  substance.  It  may  be  ex- 
tracted by  hot  alcohol,  and  obtained  as  a  light  powder,  which 
readily  absorbs  water.  It  is  an  animal  glucoside,  from  which  an 
unfermentable  sugar  may  be  derived. 


Recapitulation. 

Groups  of  unknown  molecular  structure  are  provisionally  class- 
ified: 

I.  Not  containing  nitrogen: 

(1)  As  Bitter  principles,  like  wormwood. 

(2)  As  Glucosides,  which  decompose  into  glucose  and  these. 

(3)  As  Indifferent  bodies,  like  cubebin. 

(4)  Besides  these,  are  anomalous  bodies,  like  the  bile  constituents, 

and  other  non-nitrogenous  animal  secretions. 
Chem.— 31. 


482 


ORGANIC  CHEMISTRY. 


II.  The  Nitrogenous  compounds,  or  albuminoids,  are: 

(Albumin. 
Casein. 
Blood  plasma. 

The  diffusible  albumins:  peptones. 
(1)   Albumins.  \  The  globulins. 

Lardacein. 
Insol.  in  II2O.j  The  coagulated  albumins. 

Other  derived    albumins,  as  syn- 

tonin. 

(  Collagen  products  —  glue. 
(.  Chondrogen  products — chondrin. 

Nitrogenous  substances  related  to  these,  the  soluble  ferments, 
the  haemoglobins,  and  hardened  tissues,  like  skin  and  horn. 


(2)   Gelatins 
(3) 


APPENDIX. 


CRYSTALLOGRAPHY. 

854.  Solid  bodies  are  either  amorphous  or  crystalline. 
Amorphous  bodies  are  those  which  have  no  well-defined 
geometrical  form,  as  chalk,  clay,  starch.  Crystals  have 
regular,  geometrical  figures,  bounded  by  flat  surfaces 
called  planes.  Although  the  number  of  such  figures  is 
very  great,  it  is  possible  to  group  them  all  into  six 
primary  forms,  in  each  of  which  the  bounding  planes 
are  supposed  to  be  symmetrically  disposed  about  imag- 
inary lines  called  axes.  These  axes  are  generally  three, 
which  intersect  each  other  in  the  center  of  figure. 

I.  The  isometric  or  regular  system  has  all  the  three  axes  at 
right  angles  to  each  other,  and  all  equal 
in  length.  Such  are  the  regular  octahedra, 
represented  by  the  alums;  and  the  cubes, 
represented  by  common  salt. 

FIG  109.  -^'  ^e  quadratic  or  tetragonal  system 

has  all  the  three  axes  at  right  angles  to 
each  other;  but  of  these,  only  the  two  lateral 
axes  are  equal  in  length.  No  cubes  are  possi- 
ble in  this  system,  but  they  >  are  replaced  by 
vertical  square  prisms.  The  octahedra  of  this 
system  may  have  either  form  shown  in  Fig. 
110,  or  the  vertical  axis  may  be  shorter  than 
the  lateral  axes.  FIG.  no. 

III.  The  hexagonal  system  has  four  axes.  The  three  lateral  axes 
are  in  the  same  plane,  equal  in  length,  and  inclined  to  each  other 

(483) 


484 


CHEMISTRY. 


at  an  angle  of  60°.    The  vertical  axis  is  perpendicular  to  these,  and 
may  be  either   longer  or  shorter  than  they. 
Neither  cubes  nor  octrahedra  are  possible  in 
this  system.    We  may  have  six-sided  prisms, 
like  quartz;  or  rhombohedra,  like  Iceland  spar. 


IV.  The  ortho-rhombic  or  prismatic  syxtem 
has  three  axes  all  at 
right  angles  to  each  FIG.  ill. 

other,    but    all    unequal 

in  length.     Fig.  112  represents    an    octohedron 
of  sulphur  crystallized  in  the  cold. 


FIG.  112. 


V.  The  monoclinic  system  has  three  axes 
which  may  all  differ  in  length.  The  two  lat- 
eral axes  are  at  right  angles  to  each 
other;  the  vertical  axis  is  perpendicular 
to  one  lateral  axis  and  oblique  to  the 
other.  Sulphur  crystallized  after  fusion, 

and  sodium  sulphate,  are  examples. 

L. . — *> 

FIG.  113. 
VI.   The    triclinic   or   doubly   oblique 

system  has  three  axes  which  are  all  un- 
equal and  obliquely  inclined  to  each  other. 
Such,  for  example,  are  crystals  of  cupric 
sulphate. 

NOTE.— The  student  will  do  well  to  remember 

FIC;   114  that  these  are  the  primary  forms  of  crystals.    The 

derived    forms  are  so  numerous  that  it  would 
require  a  large  treatise  to  describe  them. 

855.  Some  bodies  crystallize  in  two  forms,  as  sulphur. 
These  are  said  to  be  dimorphous.  When  different  bodies 
crystallize  in  the  same  form,  they  are  said  to  be  iso- 
morphous.  Such  are  the  arseniates  and  phosphates  of 
the  same  metal. 

The  word  crystalline  is  often  applied  to  bodies  which 
are  apparently  made  up  of  small  interlaced  crystals 
that  can  not  be  separated,  but  which  are  semi-trans- 
parent, as  quartz  rock. 


PROBLEMS. 


COMPARISON   AT  29.92   INCHES  (760  mm.)  BAROMETER. 


32°  F.  =  0°  C. 


02, 

& 

*     <n 

S*g 

§2® 

HH  $ 

£)!*§ 

SPECIFIC  GRAVITY. 

H  o  M 

H  t  2 

HfcS 

P? 

*«£• 

W  J« 

o§« 

BgB 

ks 

AIR  =  1. 

H  —  1, 

65 

BIB 

g8S 

AIR     .    . 

1.2932 

0.77 

1. 

14.43 

71.604 

30.954 

3.23 

HYDROGEN 

0.0896 

11.19 

0.0693 

1. 

4.947 

2.14 

46.73 

at 

4°C. 

pounds. 

WATER   . 

1000. 

.001 

773.2 

11160. 

8.3456 

25245.6 

.00396 

at  15°C. 

at4°C. 

819. 

25287.9 

60°  F. 


NOTE. — These  problems  are  intended  only  as  hints  of  work  that 
may  be  done.  The  teacher  may  extend  them  indefinitely;  and  may 
add  also  such*  problems  as  involve  specific  gravity,  specific  heat, 
calorific  power,  etc.  The  problems  are  carefully  graded;  and  if  the 
student  attacks  them  in  the  order  given,  he  will  find  little  diffi- 
culty in  solving  them.  It  is  taken  for  granted  that  the  bodies 
used  are  chemically  pure,  and  that  there  is  no  loss  in  manipulation. 

1.  What  is  the  weight  of  one  cubic  centimetre  of  each 
of  the  following  substances,  at  the  normal  temperature 
and  pressure? 

(a)  H;  N;  O;  Air;  Cl ;  CO;  CO2. 
(6)   H30;  CS2;  H2SO4  ;  HNO3  ;  Br. 
(c)  Li,  K;  Fe;  Ag;  Au;  Pt. 

(485) 


486  CHEMISTRY. 

What  is  the  weight  of  one  litre  of  each  of  the  above? 
What  is  the  bulk,  in  cubic  centimetres,  of  one  gramme 
of  each  of  the  above  ? 

NOTE.  —The  Law  of  Charles  is  that  the  volumes  of  all  gases  are 
proportional  to  their  absolute  temperature.  This  temperature  is 
reckoned  from  — 273°  C.,  and  is  therefore  equal  to  their  recorded 
temperature  above  zero  -f-  273°  C.;  e.  p.,  the  absolute  temperature 
of  air  at  27°  C.  is  300°  C.;  and,  at  127°  C.  is  400°  C.  Therefore, 
if  a  given  weight  of  air  measured  one  litre  at  300°  C.,  it  would 
measure  |gg=1.33  L.  at  400°  C,  absolute  temperatures. 

2.  What  is  the  volume  of  one  cubic  centimetre  of  the 
gases  in  Ex.  1,  when  reckoned  at  100°  C.?     At  50°  C.? 

NOTE. — The  Law  of  Mariotte  is  that  the  volume  of  a  gas  is  in- 
versely proportioned  to  the  pressure  to  which  it  is  subjected;  e.  ff., 
if  a  litre  of  air  taken  at  a  pressure  of  one  atmosphere,  or  7GO  mm. 
barometer,  is  subjected  to  the  pressure  of  two  atmospheres,  it  will 
be  condensed  to  _7™-  :=  —  of  its  former  value;  or,  if  the  pressure 
is  diminished  to  570  mm.,  the  volume  will  be  increased  to  |^J  =  | 
of  its  original  volume. 

3.  What  will   be   the   volume  of  each  of  the  gases  in 
Ex.    1,    when    taken    under    a    pressure    of   1140    mm.? 
Of  380  mm.  ? 

4.  What  will  be  the  volume  of  each  of  the  same  gases 
reckoned  at  100°  C.,  and  under  a  pressure  of  950  mm. 
bar.? 

5.  What  is  the  weight  of  each  element  in  ^>ne  gramme 
of  H2O?     What   is    the    bulk   of  each    in    this    weight 
taken  at  0°  C.?     What   is   the   bulk    of  each   taken   at 
100°  C.?    What  will  be  the  volume  of  the  steam  formed 
by  their  combination,   («)   reckoned    at   0°  C.  ?     (6)   At 
100°  C.  ?     How  much   pressure  will  be  required   to  re- 
duce the  latter  volume  to  the  volume  at  0°  C.  ? 

6.  Given    one   gramme   each    of  the   following   gases, 
HC1,  H2S,  H3N,  C02,  required- 

(a)  The  weight  of  each  of  the  elements  forming  these 
compounds.  (6)  The  volume  of  each  element,  (c)  The 
volume  of  the  compound. 


PROBLEMS.  487 

7.  From  the  data  given  on  p.  35,  calculate  how  many 
cubic  centimetres   of  water  will  be  required  to  form  a 
saturated  solution  containing  one  gramme  of  these  gases. 
What  will  be  the  volume  of  the  gas  absorbed?    What 
will    then   be   the   weight   of  the  solution?     Could   the 
volume    of   the    solution    be    calculated    from    the    data 
given  ?    Has  the  temperature  or  the  pressure  any  effect 
upon  the  amount  of  the  gas  absorbed  ? 

8.  How    many    grammes    of    each     element    in    100 
grammes  of  each  of  the  following?  H2O;  FeO;  Fe3O4 ; 
Fe2O3;    FeCO3;   FeSO4 ;   FeSO4, 7H2O.     Are  your  an- 
swers percentages? 

NOTE.  —  To  calculate  the  empirical  formula  of  a  compound, 
(1)  find  its  percentage  composition;  (2)  divide  each  constituent  by 
its  atomic  weight;  (3)  reduce  the  quotients  so  obtained  to  their 
simplest  ratios. 

9.  Water  yields  in  100  parts: 

RATIOS. 

2 


H     11.11  -f-    1  =  11.11 

O      88.88  -y-  16  =    5.55 
100. 


1 


The  formula  is,  therefore,  H2O.     Calculate  the  formulae 
from  the  following  data: 

(a)     N     82.35  (ft)    Fe      70. 

H    17.65  O        30. 

100.  100. 

(c)     K  28.73  (d)    Cu  57.46 

H     0.73  C       5.43 

S    23.52  H      0.91 

O   47.02  O    36.20 


100.  100. 

10.  How  many  grammes  of  Cu  are  required  to  make 
100  grammes  of  Cu2S;  CuS;  Cu2O;  CuO,CuSO4;  CuSO4, 


5H2O? 


488  CHEMISTRY. 

11.  If  one  gramme  of  K  is  taken,  how  many  grammes 
may  be  formed  of  KI ;   KC1 ;   HKO;    KHCO8 ;  K2COS  ; 
K2S04? 

12.  If  one  gramme  of  zinc  is  taken  to  make  hydrogen, 
(a)  how  much  sulphuric  acid  will  be  required?    (6)  How 
much  fl   will   be   liberated?     Its  weight?     Its  volume? 

(c)  How  much  ZnSO4  will  be  formed?    (d)  How  much 
ZnSO4,7H2O  may  be  crystallized  out? 

13.  In  making  oxygen  from  K2O,  C12O5,  what  will  be 
the  weight  of  the  products  from  100  grammes?     What, 
the  volume  of  the  oxygen  ? 

14.  Repeat  these  calculations  with  the  reactions  given 
for  the  manufacture  of  H2S;  CO2  ;  HC1 ;  Cl ;  reckoning 
each  as  in  Ex.   13  or  in  Ex.  12. 

15.  In  the  preparation  of  H2O,N2O6  from  100  grammes 
of  saltpeter,  (a)  how  much  H2SO4  is  used  when  the  salt 
remaining   is    KHSO4  ?     (6)  How  much    when   the   salt 
remaining    is    K2SO4?      (c)    Suppose    147    grammes    of 
H28O4  were  used,  what  would   be   the  salt  remaining? 

(d)  Suppose  that  no  loss  occurred,  what  weight  of  nitric 
acid  would  be  obtained?   What  volume?    (c)  Would  there 
be  any  difference  in  these  last  two  results  whether  100, 
150,  or  200  parts  of  H2SO4  were  taken? 

16.  How  many  grammes  of  FeS  are  required  to  form 
enough    H2S   to    precipitate    100    grammes    of  CuSO4  ? 
Of  Bi(NO3)3?     Of  3II2O,  As2O5?    What  will    be    the 
formula  of  the  sulphides?    Suppose  the  H2S  were  passed 
into  a  solution  of  Fe2Cl6,  how  much  sulphur  would  be 
precipitated  ? 

17.  Given  this  reaction,  2(PbO,  N2O5)  -f-  K2O,  2CrO3 
+  H20  ^  2(PbO,  Cr03)  -f  K20,  N2O5  -f  H2O,  N2O5, 
what  will   be   the   proportions   taken   and  the  products 
obtained?    If  one  gramme  of  PbO,  N2O5  is  taken,  what 
will  be  the  weight  of  the  others  ? 

18.  From   the  reaction   given  in  §212,  calculate  how 
much    of  the    two    acids    is   necessary   to   dissolve   one 
gramme  of  gold. 


PROBLEMS.  489 

19.  From  the  reactions  in  §  228,  calculate  how  much 
phosphorus  can  be  made  from  100  pounds  of  bone  ash ; 
then  from  100  pounds  of  bones. 

20.  From  the  reactions  given  on  p.  101,  calculate  the 
details   of  making  100  grammes  of  chlorate  of  potassa. 
(a)  How  much   Cl  is  required?     (6)  How  much  NaCl? 
(c)    How   much   H2SO4?     (d)   How  much   MnO2  ?     (e) 
How   much    KC1  will   be   formed?     (/)    How   can   this 
last  product  be  prevented  from  forming? 

21.  (a)  How  many  cubic  feet  in  a  room  10  feet  high, 
15   feet   long,  and   12  feet  wide?     (6)  How  many  cubic 
feet  of  oxygen  does  it  contain  ?     (c)  How  many  pounds 
of  burning   charcoal  will  consume    it   completely,   if  it 
burns   to    CO2?      (d)    How    many    pounds    of   burning 
charcoal   will   contaminate   the   air  with   five    per   cent 
of  CO 2?     (e)  How  long  will  it  take  one   adult   to   con- 
taminate it  with   two   per   cent   of  CO2?    (§302).     (/) 
How    long   will    it   take   a  gas  burner  consuming  four 
feet   of  gas   per  hour  to  contaminate   it  with  two  per 
cent  of  CO 2  ?     (#)   How  much   fresh   air  should  be  ad- 
mitted  per   hour   so   that,   with  the  adult  and  the  gas 
burner  together,  the  air  should  not  contain  more  than 
0.5  per  cent  of  CO2  ?     (A)  Reckon   the   same  from  the 
size  of  your  own  bed-room. 

22.  Determine  the  atomic  weight  of  chlorine  from  the 
following  data:    100   grammes   K2O,  C12O5  yield  60.939 
grammes  KC1;    22.032   grammes   Ag    (at.    wt.    108)    re- 
quired  15.216   grammes   KC1   for  complete  precipitation 
(at.    wt.    K  =  39.1),    14.427   grammes   KC1   gave   27.749 
grammes  AgCl. 

23.  1.586    grammes    pure    Fe    yield    2.265    grammes 
Fe2O3  :  calculate  the  atomic  weight  of  iron. 


INDEX. 


PAGE 

PAGE 

Absinthii'n     . 

.    470 

Acids  (continued). 

Acetic  acid  formulae     . 

.     292 

citric 

.     375 

manufacture,  etc. 

.     358 

coumaric    . 

.    443 

Acetic  aldehyde    . 

.    348 

cyanic 

.    311 

Acetone 

351-360 

definition  of 

.      65 

Acetylene 

.    318 

derivatives  of   . 

.        .356 

Acids     .... 

.       11 

di-hydric    . 

.    366,  371 

acetic 

292,  358 

fatty  series 

.    357 

aconitic 

.    375 

ferricyanic 

.    310 

acrylic  series     . 

.    362 

ferrocyanic 

.    310 

alphatoluic 

.     444 

formic 

.     358 

amic  .... 

.     384 

fumaric 

.    371 

amid  acetic 

.     384 

gallic 

.    441 

amid  isocaproic 

.    386 

gallotannic 

.    442 

amido  benzoic   . 

.     439 

glyceric      .         . 

.    333 

anisic 

.    441 

glycocholic 

.     471 

anthranilic 

.    440 

glycollic     . 

.    367 

aromatic    . 

.    437 

glyoxalic       "     . 

.     351 

arsenic 

.     152 

hippuric    . 

.     439 

arsenious  . 

.     151 

hydracrylic 

.     368 

atropic 

.     443 

hydriodic  . 

.     106 

basicity  of         .        . 

.      66 

hydrobromic 

.     104 

benzoic 

.    438 

hydrochloric 

.      98 

boric           .        .        . 

.     161 

hydrocyanic 

.     306 

bromic        ... 

.     104 

hydrofluoric 

.      91 

butyric 

.    361 

hydrosulphuric 

.     112 

caffeic 

.    443 

hypobromous     . 

.     104 

carbamic    . 

.    387 

hypochlorous     . 

.     100 

carbonic     . 

.     173 

iodic  . 

.        .106 

chloric 

.     101 

lactic 

.  ,      .367 

cholic 

.    471 

leucic 

.367 

chromic 

.     271 

lithofellic 

.     472 

cinnamic    .        .        . 

.    443 

maleic 

.    371 

(491) 


Adi 

IN&E& 

Alu 

PAGE 

PAGE 

Acids  (continned). 

Acids  (continued). 

malic         .         . 

.       371 

thiosulphuric    . 

.       123 

malonic     .         . 

.     370 

tropic 

,    467 

manganic  . 

t.    268 

uric    .... 

.     389 

maimitic    . 

'.     334 

valeric 

.     361 

meconic     * 

.     462 

Aconite 

.     468 

mellitic      . 

.     445 

AcroleVn 

.     349 

metaphosphorie 

.     14<i 

JEHCiilin 

.     471 

naphthoic 

,    446 

Affinity          .         .         . 

.      29 

nitric           .      '   . 

.     132 

intliKMU'cd  bv  adhesion            37 

nitro  benzole     . 

'   .    '     .     440 

electricity       ...       44 

nitrous       . 

'   .         .     13S 

heat        .     •    . 

.      38 

oleic  . 

.     362 

light       .       -. 

.      43 

organic 

.     297,  354 

relation  between,  and 

mole- 

orthophosphoric 

.     146 

cular  forces 

.      48 

oxalic 

.     369 

Alabaster       . 

.     217 

palmitic*     .      "  . 

.      •  .     362 

Albumins      .     •  . 

.     473 

periodic      . 

.         .     107 

Alcoholates        •   . 

.      ..    299 

permanganic 

•   .         .     268 

Alcohols         .      •    .     '    ; 

295,  320 

phthalic    .      '  . 

'  .  '      .444 

aromatic    .     •    .     •    . 

.     432 

picric         * 

•   .         .     427 

Aldehydes      .         . 

297,  346 

piperic       . 

.     464 

Ale                  .         . 

.     327 

propionic  . 

'  .  '       .     360 

Alizarin         .         . 

.    419 

protocatechuic  . 

.441 

Alkalamides 

.     383 

pjrbphosphoric 

'    .         .     146 

Alkalies 

10,  193 

quinic 

.     465 

tests  for     .     •    .        . 

,-    207 

rosolic     '  . 

•  ,'       ,    431 

Alkaloids      ^        .     -   . 

.    461 

ruberythric     '  . 

.     419 

Allotroj)y      . 

v      85 

saccharic    .      '   . 

'  .        .     334 

Alloxan,  alloxantin     ^ 

..    390 

salicylic      .     '    . 

.    440 

Alloys    .        ,4      •   . 

.     190 

separation  of      . 

.  .        .     364 

Allyl  alcohol         .         . 

.     331 

silicic         4     '   . 

.  •'       -.    178 

ethers         -.     •    .         . 

.     401 

stearic     '   *     '    , 

.".       .     362 

iodide      •   i     •    »     •    . 

.    397 

succinic 

s        .    370 

sulphocyanate   . 

.    401 

sulphocyanic  "  . 

.'.      .     313 

Allylene         *  .     •   .     •   . 

.     318 

sulphonic  .         . 

;     ".,  355 

Alo'in     ..-..••. 

.     470 

sulphuric  .     '    . 

'   .,    •   ..     119 

Alphatoluic  acid  .     •    . 

.     444 

sulphurous      '  . 

'  f       ..     117 

Alum    + 

.     275 

tables  of    . 

..    353,  357 

Aluminium  -^    •    .     •    . 

249,  274 

tartaric      . 

V.    .  ..    372 

hydrate      »,        . 

.    276 

taurocholic 

'  .        .     471 

oxide          «    •    *,    •    r 

,-277 

(492) 


Alu 


INDEX. 


Bar 


Aluminium  (continued), 
tests   .........     278 

Amalgams     .....     191,  237 

Amarjne        .....      .  .     436 

Amber  .....     .  .        ...    422 

Amide  compounds        .     130,  382 
Amido  benzoic  acid  .    .      ...    439 

Amine  compounds    .    .     130,  377 
Ammonia  ......      38,  128 

properties  .    .    ;    .    .        .129 
tests  .....        .        .130 

Ammonia  derivatives  .  130,  300 
Ammonium  .....  193,  204 

bromide .     207 

carbonate 205 

chloride     ....         .'   205 
hydrate      .         .         .         .204 

iodide 207 

molybdate          .        .         .     249 
nitrate        .....         .     206 

sulphate.    .     ....        .     206 

sulphide     .....        .     206 

Amorphous  bodies  defined  .  285 
Amyl.  alcohol  .  ,.  .  330 

Aniyloses  .......    337 

Analysis        23 

qualitative  and  quantita- 
tive    .....         .25 

spectrum   ....     220 

Anatto  .        .         .         ...      «     458 

Anethol         .         .        .         .437 

Anhydrides  ....       64 

acid  and  basic  .  .  .  64 
Anilides  .  .  .•'.:.  452 
Aniline  ....  451 

dyes 455 

Animal  charcoal  ...  167 
Anisic  acid  .  .  .  .  441 
Anthracene  .  .  .  .419 
Anthracite  coal  .  .  .  165 
Anthranilic  acid  .  440 


PAGE 
Antimony,  Sb       .        .     1.25,  154 

occurrence         .        ..       ,.,    154 

tests  .........    ;,.    156 

uses  *    .,...,       .*    155 
Antozone    .......  j,      85 

Aqua  regia  .         .     ...     135 

Arabin  .        .         .     ...  341 

Aragqnite      ...        .        ^    215 

Arsenetted  hydrogen    .        .     149 

tests    .....        .      .  ...  150 

Arsenic          .     ,    .         .125,  148 

organic  bases  of        .         .     380 

oxygen  compounds    .        .     151 

sulphides  .....        ..     153 

Arsenic  acid          .         .        .     152 

tests  .,  ..  .  ,.,.  .  153 
Arsenious  anhydride  .  ; .  151  • 

uses    .....        .        ,152 

Artiad  elements    .        .        .60 
Asparagin     .        ,.        .        .    .  372 

Atmosphere,  constituents  of        7 
Atom,  defined       .        .       •.,     .51 

equivalence  of  .       '  ••       .      57 
Atomicity,    graphically    ex- 
pressed       .         .         .57 
Atomic  weights     .     .    .       •.      '52 

how  obtained  .  .  .53 
A  tropic  acid  .  .  .  443 
Atropine  .  .  .  467 

Auric  chloride      .        .        .     243 

oxide  ....  244 
Aurine  ....  .430 
Aurous  chloride  .  .  .  243 

oxide  .  .  .  ..  244 
Australene  .  ...  421 
Azo  compounds  .  .  .  453 


Baking  powders 
Balsams         , 
Bar  iron 
Barium 


.     340 

•    422 

.    259 

213,  218 


(493) 


Bar 

INDEX. 

Car 

PAGE                                                                                   PAGE 

Barium  (continued). 

Bromine        .        .         .90, 

103 

chloride     .... 

219 

uses    ..... 

104 

nitrate        .... 

219 

Bromoform    . 

394 

peroxide    .... 

21  !»     Bruriiu'           .... 

466 

tests  

2U»     Butyric  acid 

361 

Bassorin         .... 

341 

Beer      

327 

Cacodyl          .... 

380 

Benzaldehyde 

435 

Cadmium       .         .              213, 

230 

Benzene         .         .         .     289, 

409  |  (tain  m           .         .         .      I«i3, 

204 

Benzoic  acid 

i:;* 

Caffeine          .... 

:;s:> 

Benzophenone       .        .    433, 

437 

Caffetannic  acid    . 

443 

Benzoyl  chloride  . 

439 

Calcium         .                 .     213, 

214 

Benzyl  alcohol 

432 

carbonate  .... 

215 

amine         .... 

451 

chloride 

917 

chloride     .... 

432 

hydrate      .... 

£t  1  / 

216 

Berzelius's  electro  -chemical 

oxide           .... 

215 

series  .... 

48 

phosphate  .... 

218 

Bessemer  process  . 

261 

sulphate     .... 

217 

Betaine          .... 

386 

Calico-printing 

460 

Bile       

471 

Calomel         .... 

234 

Binary  compounds 

15 

Camphors      .... 

421 

Bismuth         .        .        .125, 

157 

Can  th  arid  in  .... 

471 

compounds 

158 

Caoutchouc  .... 

423 

uses    

157 

Carbarn  ic  acid 

387 

Bitter  principles  . 

470 

Carbarn  ides  .... 

387 

Bituminous  coal  . 

165 

Carbamines  .... 

383 

Black  band  .... 

256 

Carbohydrates       .        .       87, 

336 

Blende  

228 

Carbon  .         .        .        .     163, 

164 

Blood-plasma 

473 

allotropic  states 

164 

Blue  vitriol  .... 

240 

chemical  properties  . 

168 

Bohemian  glass    . 

282 

hydrogen  compounds     164, 

285 

Borax    .         .         .         .        . 

160 

oxygen  compounds  . 

169 

uses   ..... 

161 

physical  properties  . 

164 

Boric  acid     .... 

161 

Carbonic  anhydride      .        8, 

171 

test     

162 

physiological  properties    . 

174 

Borneo  camphor  . 

422 

tests    

175 

Boron    ..... 

160 

uses    ..... 

174 

Braunite        .... 

267 

Carbonic  disulphide     . 

175 

Brazil  wood  .... 

459 

176 

Bread-making       .         .- 

339 

Carbonous  oxide  . 

169 

Bricks    . 

280 

physiological  properties    . 

171 

(494) 


Car 


INDEX. 


Con 


Carmine 
Car  nine 
Carotin 
Casein   . 
Cast  iron 
Catechol 
Cellulose 
Cerebrin 
Cerium 
Cetyl  alcohol 
Cevadine 
Cheese    . 


PAGE 

459 
385 
471 
473 
258 
428 
337 
481 
231 
330 
468 
476 


Chemical  affinity,  character- 
istics of  .        .26 
Chemical  philosophy    .         .       50 
Chemical  properties  of  met- 
als      ....     189 
Chemical  re-agents,  action  of    361 
Chemistry,  definition  of       ..      12 
Chinchona  group          .         .     464 
Chinchonine           .         .         .     465 
Chinoline  bases     .        .        .     466 
Chloral          .        .        .        .349 
Chlorates       .        .        .        .101 
Chloric  acid          .  '      .        .101 
Chloric  peroxide  .         .         .     102 
Chloride  of  lime  .        .        .100 
Chloride  of  soda  .        .        .100 
Chlorine        ...        90,  93 
combination       ...       95 
displacement  by  .95 
indirect  oxidation     .         .       97 
oxygen  compounds   .         .     100 
properties  of      .        .        94,  95 

uses 97 

Chlorochromic  anhydride  .  272 
Chloroform  .  .  .  .394 
Chlorophyll  ....  458 
Cholesterin  ....  433 
Cholic  acid  .  .  .  .471 
Choline  386 


Chondrogen  . 
Chrome  iron 
Chromic  acid 

anhydride 

chloride     . 

hydrate 

oxide 

sulphate  . 
Chromium  . 

tests  . 


PAGE 

.  479 

.  269 

.  271 

.  270 

.  273 

.  272 

.  272 

.  273 

249,  269 

,  274 


uses 273 

Chrysene  .  .  .  .420 
Cinnabar  .  .  .  .232 
Cinnamic  acid  .  .  .  443 
aldehyde  .  .  .  .436 
Cinnyl  alcohol  .  .  .433 
Citric  acid  .  .  .  .375 
Clay  iron  stone  .  .  .  256 

Coals 165 

Coal-tar  products          .         .     413 

Cobalt  ....     249,  251 

chloride     ....     253 

nitrate        .        .         .        .252 

tests 255 

Codeine         ....     464 

Co-efficient  of  absorption     .       35 

Cohesion        .         .  27 

of  metals  .        .         .         .186 

Colchicine     .         .         .         .468 

Cold  shortness      .        .        .260 

Collagen        .        .        .        .479 

Collodion      .         .         .         .338 

Color  of  metals    .        .        .186 

Combination          ...       15 

energy  of  .         .         .        .25 

heat  of  .  .41 

Combining  proportions,  law 

of  ....  19 
Combustion  ....  40 
Compounds,  notation  of  .  68 
Coniferin  .  434 


(495) 


Con 


INDEX. 


Eth 


PAGE 

PAGE 

Conine  .        .         .         . 

462 

Dial  u  ram  ide 

.     390 

•Constant  proportions,  law  of 

17 

Diamond       .         . 

.     164 

Constituents  of  atmosphere  . 

7 

Diazo  compounds 

.    453 

of  primary  rocks 

27 

Didymium     .         . 

.     231 

Copper  ......     213, 

237 

Dimorphous  bodies 

.     484 

properties  of      .         . 

238 

Distilled   liquors  . 

.     329 

Copperas       .         . 

264 

Double  decomposition 

.      22 

Correlative  forces 

48 

Double  salts      .... 

.      20 

Corrosive  sublimate      .         < 

235 

Dualistic  form  u  he 

63,  68 

Corundum     ....        % 

277 

Dualistic  theory  . 

.      63 

Cou  marie  acid       . 

443 

Dulcite           ..... 

.    334 

Coumarin       .... 

443 

Dyeing,  art  of 

.    459 

Creatine        ...... 

385 

Dyes,  aniline 

.    455 

Creatinine      .        . 

385 

azo  and  diax.o   . 

.    453 

Crystalline  form  of  im-tals  . 

186 

cocjiineal    . 

.     459 

Crystallography    . 

483 

indigo 

.    456 

Cubebin        .... 

471 

madder       ..... 

.     419 

Cumene          .         . 

415 

phenol 

.    430 

Ctimyl  alcohol      .    .     .    .     < 

433 

vegetable    . 

.    458 

Cupric  carbonates 

240 

Efflorescence 

..      68 

nitrate        ....        . 

240 

Elastjn           ... 

.     481 

oxide          ... 

239 

Electro-chemical  series 

.      48 

sulphate     .... 

240 

Electrolysis  .        ... 

.      45 

sulphide     .... 

231) 

Elements,  art  i  ad  .         .  . 

.      60 

tests  for     .... 

241 

number  of          . 

.      12 

uses  of        .... 

240 

perjssad     . 

.      59 

Cuprous  chloride 

239 

state  of.     ... 

.      28 

oxide          «... 

239 

table  of.     .         .         12 

,  59,  192 

Curarine        . 

467 

Emetine         ..... 

.    468 

Cyanates       ^   .    ,: 

311 

Einulsin         .        »  ,       . 

343,  434 

Cyanides        .         .         . 

308 

Eosin     .... 

.    431 

Cyanogen      ..... 

307 

Epichlorhydrin 

.    397 

Cyanogen  compounds  .     305, 

311 

Epsom  salts 

.     227 

Cyanogen  ethers   . 

398 

Erbium          .        . 

.    231 

Cymene          ... 

416 

Erythrite       .        .         . 

.     334 

Eserine 

.     467 

Decay  and  fermentation 

324 

Ethane           ..... 

.     317 

Decomposition  by  heat 

39 

Ethene  glycol 

.     332 

Deliquescent  bodies 

35 

Ethereal  salts 

355,  402 

Dextrin 

340 

Ethers,  classes  of 

298,  392 

Dextrose        .... 

342 

preparation  of  . 

.    398 

(496) 


Eth 

INDEX. 

Hal 

PAGE 

PAGE 

Ethyl  acetate 

.    405 

Galena  . 

.     222,  224 

alcohol 

.    323 

Gallic  acid    . 

.    441 

chloride     . 

.    394 

Gallium 

.     278 

ether 

.    400 

Gallotannic  acid  . 

.        .    442 

nitrite  and  nitrate     . 

.    403 

Gangue 

.    257 

sulphate    . 

.     403 

Garancine 

.    420 

sulphite     . 

.    404 

Gelatin 

.    479 

Ethylamine  . 

.    380 

Glass 

.     282 

Ethylene 

.    318 

manufacture 

.    284 

chloride 

.    395 

varieties  of 

.    179 

Euchlorine    . 

.     102 

Glauber's  salt 

.    196 

Eugenol 

.    434 

Globulins 

.    474 

Glucinum 

.    231 

Glucose 

.    341 

Fats       .... 

.    362 

Glucoses 

.    341 

table  of,  and  of  oils 

.    424 

Glucosides     . 

.        .343 

Fermentation         . 

.    324 

Glue      . 

.    479 

Fermented  liquors 

.    327 

Gluten  . 

.    475 

Ferments 

.    477 

Glycerine,  glycerol 

.    332 

Ferric  sulphate     . 

.     264 

Glychocollic  acid 

.    471 

Ferricyanides 

.    309 

Glycocine 

.    384,  472 

Ferrocyanides 

.    309 

Glycollic  acid 

.    367 

Ferrous  carbonate 

.     265 

Glycols 

.    331 

sulphate     . 

.     264 

Glyoxal         .    '    . 

.    350 

Fibrin   

.    474 

Glyoxalic  acid 

.    351 

Fibrinogen    . 

.    475 

Gold      . 

.     242,  243 

Fibrinoplastic        .         . 

.    475 

tests   .        . 

.     244 

Fluorescein   . 

.    431 

uses    . 

.    244 

Fluorine 

90,  91 

Graphite 

.165 

Force  indestructible      . 

.      49 

Gray  iron 

.     259 

Formic  acid  . 

.    358 

Green  vitriol 

.    264 

aldehyde    . 

.     348 

Gum  resins  . 

.    422 

Formulae,  explained 

56,  63 

Gums     . 

.    341 

Fruit  ethers 

.    405 

Gunpowder    . 

.    203 

Fuchsine 

.    455 

Gutta  percha 

..       .    423 

Fulminates   . 

.    312 

Gypsum 

.    217 

Fumaric  acid 

.    371 

Furfurol 

.    350 

Hsemaglobin 

.    478 

Fusel-oil 

.    330 

Hsematin 

.479 

Fusibility  of  metals     . 

.     187 

Hsematoxylin 

.    459 

Fustic   .         .         . 

.    459 

Halogens 

.90 

Chem.—  32. 

(497) 

Cal 


INDEX. 


Ian 


\ 

PAGE 

PAGE 

Haloid  ethers 

.    392    Indican 

343,  456 

Haloid  salts 

66,  90    Indigo  group 

.     456 

Heat,  developed  by  combina-             Indium 

.     242 

tion 

.       42    Indole    .... 

.     457 

Heavy  spar  . 

.     218    Ink 

.     442 

Hematite 

1  Ai! 

Hippuric  acid       .         .     390,  4:>!'    Iodine    .... 

iuo 
90,  104 

Hydraerylic  acid 

.     368        oxides  of   . 

.     106 

Hydramides 

.     435        properties 

.     105 

Hydnuins 

.     454        uses    .... 

.     106 

Hydrins         .         . 

.     397  :  I  rid  iu  in 

.     245 

Hydriodic  acid 

.     106    Iron       .... 

249,  255 

Hydrocarbons,  open  chain 

.     31.")        affinities  for  sulphur 

.     265 

benzene,  etc. 

.    414  1      compounds 

.     263 

Hydrochloric  acid 

98        manufacture 

.     257 

Uses      .... 

99       ores    .... 

.     256 

Hydrocyanic  acid 

.     306  ;      oxides 

.     265 

Hydrofluoric  acid 

JU  ;      tests  for     . 

.     266 

properties  . 

92        uses    .... 

.     263 

Hydrogen 

10,  71     Isatin,  isatyde 

.    457 

312 

physiological  properties 

77    Isomerism 

.     293 

properties  . 

73,  75        by  position 

.     410 

reducing  agent  . 

7(5    Isomorphous  bodies 

.     484 

uses    . 

Hydrogen  peroxide 
Hydrogen   silicide 
Hydrogen  sulphide 
Hydroquinone 
Hydroxides,  hydrates 
Hydroxylamine     . 
Hyoscine 
Hyoscyamine 
Hypochlorites 
Hypophosphites    . 
Hyposulphites 

Iceland  moss 
Iceland  spar 
Ignition,  temperature 
India  rubber 


of 


.  89 

.  177 

.  112 

.  428 
64,  87 

.  379 

.  468 

.  468 

.  100 

.  145 

.  123 

.  340 

.  215 

.  38 

423 


Jervine 

Keratin 
Ketones 
Koumiss 
Koiissj  n 

Lac 

dye    . 
Lactic  acid 
Lactose 
Lactuceriu 
Lsevulose 
Lagunes 
Lampblack 
Lanthanum 


.  468 

.  481 

298,  351 

.  344 

470 


361, 


422 
459 
367 
343 
470 
342 
160 
167 
231 


(498) 


Lap 


INDEX, 


Met 


] 

^AGE 

PAGE 

Lapis  lazuli 

277 

Maltose 

.     344 

479 

AI  clll  2TR11GSG 

24Q    9fi7 

Law  of  Avogadro 

51 

tests  and  uses  . 

268,  269 

Law    of   combining   propor- 

Mannite 

.     334 

tions        .... 

19 

mannitic  acid  . 

.     334 

constant  proportions 

17 

Marsh's  test 

.     149 

multiple  proportions 

18 

Mass,  influence  of 

.      29 

Laws  of  Berthollet       .         36 

,  37 

Meconic  acid 

.     462 

Lead      .         .        .             4>13 

222 

Meconine 

464 

alloys         .... 

225 

Mellitic  acid 

.     445 

carbonate  .... 

223 

Mendelejeff,  table  of    . 

191,  192 

chloride     .... 

223 

Menthol        .         . 

.    422 

chroinate  .... 

271 

Mercuric  salts 

.     235 

nitrate       .... 

223 

chloride     . 

.     235 

sulphide     .... 

224 

iodide 

.     235 

tests  

225 

nitrate 

.     235 

Leather          .... 

443 

oxide 

.     235 

Lecithins       .         . 

407 

sulphide    . 

.     236 

Legumin       .... 

476 

tests  .... 

.     237 

Leucic  acid  .... 

367 

Mercurous  salts   . 

.     233 

Leucine         

386 

chloride     . 

.     234 

Light,  use  in  photography 

44 

iodide 

.     234 

Lignite          .... 

165 

nitrate 

.     234 

Lithium        .         .         .     193, 

207 

oxide 

.     234 

Logwood       .... 

459 

tests  .... 

.     237 

Luster  of  metals  .         . 

185 

Mercury 

213,  232 

Mesitylene    . 

352,  416 

Magnesia  alba 

227 

acids  of     . 

.    444 

Magnesium   .         .         .     213, 

226 

Metals,  characteristics 

.      14 

carbonate  .         .         . 

227 

natural  history 

.     188 

chloride     .... 

227 

organo-compounds    . 

.     381 

oxide         .... 

226 

physical  properties  . 

.     185 

phosphate 

228 

specific  gravity 

.     188 

sulphate    .... 

227 

Metaphosphoric  acid   . 

.     146 

Magnetite     .... 

256 

Metathesis    . 

.      22 

Malachite     .... 

237 

Methane 

.     317 

Maleic  acid 

371 

Methyl  alcohol     .    .     . 

.     323 

Malic  acid    .... 

371 

acetate 

.     404 

Malleability  of  metals 

187 

chloride     .         .         . 

.     393 

Malleable  iron 

261 

ethers         .... 

.    400 

Malonic  acid 

370 

Methylamine 

.     379 

Mic 


INDEX. 


Oxy 


PAGE 

PAGE 

Microcosm  ic  salt 

.     206 

Nitrogen  (continued). 

Milk  sugar  . 

.     344 

oxides        .        .        .18, 

131 

Mineral  coal 

.     165 

uses  ..... 

128 

Mixture 

.       16 

Nitrogenous  bodies 

205 

Molecular  volume 

51,  53 

Nitro  prus^ides    . 

311 

Molecules     . 

.      51 

Nitrous   acid 

138 

Molybdenum 

.     249 

Nitrous  anhydride 

137 

Morphine 

.     463 

Nitrous  oxide 

135 

Mucus 

.     479 

properties 

136 

Multiple  proportion 

s,  law  of      18 

Nitryl  . 

140 

1*4 

Murexide 

.     390 

Noble  metals 

245 

Mustard-oils 

.     313,  402 

Non-metals,  characteristics  . 

14 

Myosin 

.     474 

Nordhausen  acid,  uses 

123 

My  rosin 

.     402 

Notation  and   nomenclature 

62 

Notation  of  compounds 

68 

Naphthalene 

.     418 

Nuclei'n         .... 

481 

Naphthlamine 

.     454 

Naphthols     . 

.     434 

Oils  and  fata 

424 

Narcotine 

.     464 

Oleliant  gas 

318 

Nascent  state 

.      31 

Olefmes         .... 

317 

Natural  history  of 

metals  .     188 

Oleic  acid     .... 

362 

Nessler's  test 

.     130 

Opacity  of  metals 

185 

Neurine 

.     386,  407 

Opium  ..... 

462 

Nickel 

.     249,  251 

Orcinol          .... 

430 

sulphate    . 

.     252 

Organic  chemistry,  defined  . 

164 

testa  . 

.     255 

Organic  substances 

285 

Nicotine 

.     462 

imperfect  combustion  of  . 

166 

Niobium 

.     125 

Orientation  .... 

410 

Nitric  acid  . 

.     132 

Orpiment      .... 

153 

properties 

.     133 

Orthophosphoric  acid  . 

146 

uses  . 

.     135 

Osmium        .         .         .     245, 

246 

Nitric  anhydride 

.     134 

Oxalic  acid 

369 

Nitric  ethers 

.     403 

ether          .... 

405 

Nitric  oxide 

.     136 

Ox-bile          .        .    •     . 

386 

properties 

.     136 

Oxygen          .        .    9,  71,  78, 

108 

Nitric  peroxide    . 

.     139 

allotropic  states 

85 

Nitrils  . 

.     383 

in  atmosphere  . 

82 

Nitro  benzenes     . 

.     450 

properties 

79 

derivatives 

.     449 

tests  

81 

D«ir<iffi.ns 

397 

81 

Nitrogen 

9,  125,  126 

Oxyljsemoglobm    . 

478 

(500) 


Oxy 


INDEX. 


Pyr 


PAGE 

PAGE 

Oxysalts        .... 

66 

Platinum  (continued). 

Ozone    ..... 

84 

tests  .... 

248 

tetrachloride      . 

.     247 

Palladium     .         .         .     245, 

247 

Polymerism  . 

.     294 

Palmitic  acid 

362 

Porcelain 

.    281 

Para-albumin 

479 

Potassium 

193,  199 

Para-aldehyde 

348 

aluminiate 

.     277 

Para-chloral 

349 

bicarbonate 

.     201 

Paraffins        .... 

316 

bichromate 

.     270 

Parchment  paper 

338 

carbonate 

.     200 

Pectose          .... 

341 

chlorate  . 

.    101 

Pepsin  

477 

chloride 

.    202 

Peptones        .... 

477 

chromate   . 

.    270 

Periodic  acid 

107 

hydrate 

.    201 

Perissad  elements 

.  59 

nitrate 

.     202 

Phenanthrene 

419 

perchl  orate 

.     103 

Phenols          .... 

425 

permanganate   . 

.     268 

Phenyl  hydrazin  . 

454 

sulphate    . 

.     204 

Phloroglucol 

430 

sulphides  . 

.     202 

Phosphines   .... 

380 

Precipitate    . 

.      36 

Phosphorus  .         .        .     125, 

140 

Precipitation 

.      36 

allotropic  states 

142 

Problems 

.    485 

hydrogen  compounds 

143 

Processes  of  chemistry 

.      14 

occurrence 

140 

Proof  spirit  . 

.    329 

oxygen  compounds   . 

144 

Propane 

.     317 

properties  .... 

141 

Propionic  acid 

.    360 

tests  .        .        .        ... 

143 

Propylamine 

.    380 

uses   

142 

Propylene 

.    318 

Phosphurretted  hydrogen    . 

143 

Protein  substances 

.     473 

Photography 

210 

Protocatechuic  acid 

.    441 

Phthaleins    .... 

431 

Prussian  blue 

.     266 

Phthalic  acid 

444 

Ptomaines     . 

.    467 

Physostigrnine 

467 

Purpurine     . 

.     420 

Picric  acid    .... 

427 

Pyrene  .... 

.    420 

Picrotoxin     .... 

470 

Pyridine  bases 

.     461 

Pilocarpin     .... 

468 

Pyrocatechin  (catechol) 

.     428 

Piperic  acid 

464 

Pyrogallol     . 

.     430 

Plaster  of  Paris   . 

217 

Pyrolusite 

.     267 

Platinum       .         .         .     245, 

247 

Pyrophosphoric  acid     . 

.     146 

ammonio-chloride 

248 

Pyrrol  (note) 

.    469 

black          .... 

247 

(501) 


Qua 


IXDEX. 


Sod 


Qualitative  analysis 
Quantitative  analysis 
Quercetin 
Quicklime     . 
Quinhy  drone 
Quinidine 
Quinone 

Radicals 

Reactions 

Re-agents 

Realgar 

Recapitulation,  alkalu 

atoms 

boron 

carbon  group    . 

clieiiiical   affinity 

chlorine  group 

dyad  metals 

hexad  metals     . 

hydrogen,  oxygen,  w 

keramics  and  glass  , 

metals 

nitrogen  group 

sulphur  group  . 

tetrad  metals     . 
Red  orpiment 
Red  shortness 
Resins  ... 
Resorcinol     . 
Rhodium 
Rinman's  green    . 
Rosaniline     . 
Rosolic  acid 
Ruberythric  acid 
Rubidium     . 
Ruthenium    . 

Saccharic  acid 
Saccharose    . 
Safflower 


PA<!E 

25    Saffron 

2~>    Salicin,  saligenin 
.     471    Salicylic  acid 
.     215        aldehyde    . 
.     429    Sal  soda 
.     405  !  Salts  defined 
.     4(55  !  Salts  of  organic  aci«U 

•  Santonin 
61,  62  |  Sarcine 

22    Sarcosine 

'2'2    Si'lrnium 
153   Semi-metals  . 
.     "21  "2  .  Sericin 

69  '  Scries  d 


66, 


fined 

1(52  '      compared  . 
1S4    Signs  of  evolution 


PA(!K 

459 
434 
440 
436 
197 
190 
355 
470 
385 
385 
108 
13 
481 
287 
447 


and 


pre- 


491 


cipitation 


iter 


107  Silicates 
241  '  uses  . 
278  '  Silicic  acid  . 

89    Silicic  anhydride 
284  I      properties 
191  j      tests  . 
1,58  j  Silicon  . 
124  !  Silver    . 


.     218 

.     153 

.     260 

.     422 

.     428 

245;  246 

.     253 

.     455 

.     431 

343,  419 

193,  204 

245,  246 

334 
.    343 

,     459 


bromide     . 

chloride 

iodide 

nitrate 

oxide 
Sinapine 
Sincaline 
Skatol    . 
Smalt    . 
Smithsonite  . 
Soaps     . 
Sodium 

bicarbonate 

carbonate  . 

chloride 

hydrate 


.  23 

.  179 

.  179 

.  178 

.  177 

.  178 

.  180 

163,  176 

193,  208 

.  210 

.  210 

.  210 

.  209 

.  210 

.  464 

.  386 

.  457 

.  253 

.  228 

.  365 

193,  194 

.  197 

.  197 

.  196 
198 


(502) 


Sod 

INDEX. 

Tes 

PAGE 

PAGE 

Sodium  (continued). 

Sulphurous  acid  . 

117 

nitrate        .... 

198 

Sulphurous  anhydride 

115 

phosphate 

198 

uses    . 

118 

reducing  agent 

195 

Synthesis       .... 

15 

silicates      .... 

198 

examples  of       ... 

483 

sulphate    .... 

196 

Syntonin        .... 

476 

Solanine         .... 

468 

Solution         .... 

32 

Table  of  acids      .         .      353-357 

chemical    .... 

34 

atomic  heats 

55 

simple        .... 

33 

co-efficient  of  absorption  . 

35 

Solvents         .... 

34 

condensible  gases 

28 

Sparteine 

462 

elements       ..         -12,  59, 

192 

Spathic  iron 

256 

heat  of  combination 

42 

Specific  gravity  of  metals  . 

188 

of  Mendelejeff  .         .     191, 

192 

Spectroscope 

220 

properties  of  metals 

187 

Spectrum  analysis 

220 

Tannins         .... 

442 

Specular  iron 

256 

Tantalum      .         .         .         . 

125 

Spiegel-eisen 

259 

Tartaric  acid 

372 

Spirits  of  nitre     . 

403 

ethers         .... 

407 

Spongy  platinum 

247 

Taurocholic  acid 

471 

Stannic  chloride,  oxide 

182 

Tellurium      .         .         .     108, 

109 

Stannous  chloride 

181 

Temperature  of  ignition 

38 

oxide          .... 

182 

Ternary  compounds 

20 

sulphide     .... 

183 

Terpenes        .... 

420 

Starch    ..... 

338 

Tests,  alkalies 

207 

Stearic  acid  .         .         . 

362 

aluminium 

278 

Strychnine    .... 

466 

ammonia  .... 

130 

Sublimation  .... 

24 

antimony  .         .         .  • 

156 

Substitution 

21 

arsenic       .... 

150 

Suffoni  ..... 

160 

arsenic  acid 

152 

Sugar  of  lead       .         .     •    . 

360 

barium       .... 

219 

Sugars  . 

336 

boric  acid 

162 

Sulpho  salts 

67 

carbonic  anhydride  . 

175 

Sulphur         .         .         .     108, 

109 

chromium 

274 

haloid  compounds 

124 

copper        ,        i        .        . 

241 

occurrence 

109 

gold   .... 

244 

oxides        .... 

114 

iron    ..... 

266 

tests  and  uses  .         .     Ill, 

112 

lead    ..... 

225 

Sulphuric  acid 

119 

magnesium  group     . 

231 

properties,  uses          .     121, 

122 

manganese 

269 

Sulphuric  anhydride   . 

118 

mercury     .... 

237 

(503) 

Tes 

INDEX. 

Zir 

PAGE 

PAGE 

Tests,  alkalies  (continued). 

Vanadium    . 

125,  126 

nickel  and  cobalt 

255  1  Vanillic  alcohol    . 

.     434 

oxygen       .... 

81    Vanillin 

.     437 

ozone          .... 

84    Veratrum  group  . 

.     468 

phosphoric  acid 

147    Verdigris 

.     360 

phosphorus 

143    Vitellin 

.     474 

platinum   .... 

248 

silicic  anhydride 

180    ... 

rwv«* 

sulphur      .... 
tin      

>»  ad      .         .        .        .         .     -o  / 

Water,  chemical    proj>erties 
1  S3                f                                                    __ 

of    . 

87 

water          .... 

Thallium       .... 
Thenard's  blue 
Tbeobromine 

constituents 

-4L>        distilled 
253                .     . 
f  i       physical  properties  . 

.  ix-  »                                  *    . 

9,  71,  85 
.       88 
.       86 

Theory,  dualistie 

potable 

63            .. 

.       88 

Thermal  unit 
Thiocarbonic  ethers 

41 
405 

saline  matters  in 
synthesis  of 

.       88 

.       45 

Thio-e  there   .... 

Thiosulphuric  acid 
Thorinum      .... 

401 
123 
231 

Water  of  constitution  . 
of  crystallization 
Whisky 
White  iron    . 

68,  87 
68,  87 
.     329 

.     258 

Tin        .        .        .        .     163, 
properties,  uses 

ISO 
1S1 

Wintergreen,  oil  of 
Wi  thorite 

.     440 
.     218 

tests  
Titanium       .         .         .164, 
Toluene         .... 

183 
184 
415 

Wood's  metal 
Wrought-iron 

.     230 
.     259 

Toluidine      .... 

452 

Tri-nitro  glycerine 
Tropic  acid  .... 
Tungsten       .... 

333 
467 
249 

Xanthates 
Xanthine 
Xylenes 

.     406 
.    385 
.     416 

Turnbull's  blue     . 

266 

Tuyeres          .... 

257 

Yeast     .... 

.     326 

Typical  formula' 

56 

Yttrium 

.     231 

Tyrosine        .         .        .     386, 

443 

Zinc       .... 

213,  228 

Ultramarine 

277 

alloys 

.     230 

Uramil           .... 

390 

carbonate  . 

.     230 

Uranium       .         .         .     249, 

250 

chloride 

.     229 

Urea              .... 

388        hydroxide 

.    229 

Uric  acid      .... 

389 

sulphate     . 

.     229 

sulphide    . 

.     230 

Valeric  (valerianic)  acid     . 

361    Zirconium     . 

163,  184 

(504) 


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1707 


237443 


Y] 


